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Can You Really Have 2 Anti-Viral Programs on One Computer?

by analyzerbunny / September 20, 2008 3:01 AM PDT

My desktop computer was recently taken down by a virus and was in the shop for week getting reformatted and fresh OS install of Windows XP Professional with Service Pack 3.

The computer technician recommended I keep the Avast program he had installed on the computer and to use Fix It 8 as a utility and its anti-viral program as a back up but to make sure they weren't both running at the same time.

As it turned out, I wasn't able to get Fix It 8 back on my desktop after uninstalling it for troubleshooting purposes and decided to check out ESET NOD 3.0 as an alternative back up antiviral program.

ESET told me to make sure I uninstalled any antivirus programs on my computer before installing ESET because it could cause system instability, apparently, even if both of the programs are not running simulataneously.

So, what options do I have?

Is it too risky to have a second antivirus program on one computer even if they are not running at the same time?

If one can have two antivirus programs, does it matter which 2 programs you have?

I'd love to get opinions from people about this and any suggestions would be greatly appreciated.

Thanks so much!

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It is usually only one anti-virus - not two but

There are at the top, virus scans that are free to use. Save a link in your favorites. Darrell

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My thoughts and opinion...
by glenn30 / September 20, 2008 5:37 AM PDT

I see no problem having two anti-virus programs on the computer but only one should be active and running... the other can be used on demand but even then I would shut down or disable the other while a scan in in progress.

AFAIK it does not matter which anti-virus programs are used... there are plenty of free ones that should do just fine. I am presently using Avast and have used AVG in the past... never any problems with viruses or malware.

Hope this helps.


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Thanks, Glenn...
by analyzerbunny / September 21, 2008 2:51 PM PDT

Thank you for the feedback.

I'll download AVG again.

AVG was on my laptop before, but I uninstalled it when I installed Avast thinking I couldn't have the two programs on the same computer.

So, I really appreciate your comment.

Thanks, again.

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Don't do it.
by DADSGETNDOWN / October 4, 2008 8:28 PM PDT
In reply to: Thanks, Glenn...

Don't do it.
Don't get AVG.
and don't install 2 ANTIVIRUS.
I loved AVG.
Get something else.
Me ? I use AVAST! now too, very good.

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You didn't read what I said...
by glenn30 / October 4, 2008 10:47 PM PDT
In reply to: Don't do it.

Only one anti-virus should be "ACTIVE AND RUNNING" at the same time... I see no problem having two but NOT running at the same time as there could be conflicts with each fighting for supremacy rights.

Makes a big difference!


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he is right
by merrittolsen / October 1, 2011 1:52 PM PDT
In reply to: Don't do it.

listen to him or find out the hard way like i did when i had to have my laptop repaired because the 2 AV's caused my OS to crash....

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by ramarc / September 22, 2008 10:59 AM PDT

you can have two if you're paranoid, but you should not have 2 active anti-virus products since you'll be needlessly slowing down your pc.

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I'm running two.
by Walter Harvey / September 22, 2008 4:42 AM PDT

I'm running Windows Defender and Spyware Doctor, both active, and having no problems whatsoever. Every so often a window pops up from Windows Defender telling me I should only have one av running at a time and asking if I want to close Defender. I just say no and things continue without incident.

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You can have more than...
by Larry38 / September 22, 2008 5:33 AM PDT
In reply to: I'm running two.

one Anti-Spyware Program running at one time, however only one AV.

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Those are antispyware. NOT A/V
by DADSGETNDOWN / October 4, 2008 8:31 PM PDT
In reply to: I'm running two.

Sorry not offense.
Those are "Antispyware" or "Spyware" programs.

They are NOT "Antivirus"
2 completely different programs.

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Be careful...........
by trojan destroyer / September 22, 2008 5:25 AM PDT

Hi analyzer, i'm afraid that some of the very helpful advice you have been receiving is not entiraly correct
It is ok to have more then 1 Antispyware program on your computer as there is NO conflicts resulting in system instability, but an Antivirus app works differently, based on the current technology they work based primarily on signature detection as well as sophisticated heuristic algorithms which i wont go into right now, so in effect an antivirus application works because they are using real viruses to detect viruses!! so if you have 2 antivirus installed on your system it WILL cause system instability as they will both think the other program is an actual virus! and not 1 of the good guys, this not only will use up huge amount of your system resources, but will slow your computer right down to a crawl, and cause system conflicts and instability, so my advice will be to only have 1 Antivirus installed at a time, and multiple antispyware for good backup! all the best hope this helps

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Two real-time antispyware
by Someones / September 23, 2008 6:45 PM PDT
In reply to: Be careful...........

I've heard that more than one real-time antispyware is also not good. There'll be no obvious conflicts, but they could actually stop each other from detecting malware. I'm not too sure of the details myself, but it was from a trustworthy source.

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learned the hard way
by merrittolsen / October 1, 2011 1:56 PM PDT
In reply to: Be careful...........

my system crashed and would not boot windows and i had to have my hard drive wiped and restored to factory settings...my advice is DON'T DO IT!! i am $229 poorer but wiser after my OS crashed..

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by GEO2003 / September 22, 2008 5:39 AM PDT

It is not recommended, because Antiviruses lock themselfs at the kernel level.
One type of programing might see the other as a threat, hence creating a conflict on the boot process.
Or it may simple see the other antivirus as a competing application and try to disable one another, again creating a conflic.
Even if both work together it will slow down your pc.

Why would you want to have to when one well design, should do the job.

Try using AVAST HOME EDITION FREE, from www.avast.com.

It has seven shields that cover all, Antivirus/Antispyware/Antirootkit, email checking(client or online), p2p checking, web shield, general shield, chat shield.

It works fantastic with XP and Vista.

You can even stop MS Window Defender, but this one does not conflict with AVAST.

PCTOOLS, Antivirus/Antispyware Free edition does not conflict with AVAST either.
The free version of this can only be downloaded from Google Applications even if you don't download any of Google applications.
However, pctools application wants to constantly send information about your usage to pctools so that they can keep track of how many infections they have stopped.
This to me is too intrusive and really don't need it with AVAST.

AVAST is also free, you need a key but the only thing they request for you to get your key is your email address.
And to renew it every years.

No big deal for the protection AVAST provides for free.

For a review on Avast got pcmag.com and search for Avast Reviews.

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Definitely YES to Avast over AVG!!!
by btljooz / September 22, 2008 6:39 AM PDT

Avast saved my computer just yesterday! However, I do back it up with an online scanner like the Symantec one given above.
Only I use F-Secure (rated second only to Symantec):


Hope this helps. Good Luck! Grin

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Yes to Avast..
by jjuujj / September 22, 2008 6:58 AM PDT

I have been using Avast for some time now and it has never let me down...I mean perhaps I have never come across a virus that this guy couldn't catch, but that is all I know......no problems......another spyware catcher I like is Advanced Windows Care (free-version)...it does about 7 different functions with one push of a button, and does it well and has never caused a problem or conflict, low on resources and it just plain works well.....It catches some things that Ad-aware, spy-bot R*D, crap cleaner, e-z cleaner and some others didn't do too well with.....highly recommend Avast and Advanced Windows Care.......


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by trojan destroyer / September 22, 2008 7:15 AM PDT
In reply to: Yes to Avast..

Yes you may be full of praise for avast but you havent actually answered the guys question about running 2 antivirus apps at the same time, lol, and while were on this topic avast dosent hold the highest detection for detecting viruses, i'm afraid that honor belongs to AVIRA which is also free check out http://www.virusbtn.com/news/2008/09_02.xml

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Avast or Avira
by btljooz / September 23, 2008 3:49 AM PDT
In reply to: huh?

OK, first off, the poster you answered was merely commenting on my post, which was commenting on an answer given to the original question. There is no reason to malign him for that.

Second, I have used both Avast and Avira on separate machines at the same time to compare the two before deciding on one or the other. Therefore, I have experience with both programs. (Do you? Confused ) BTW: I quit using AVG several years ago when it became bloated and allowed my machine to get such a bad infestation that I had to replace not only the software but the hardware as well. Plain That was back when it first became fashionable to hack innocent web pages and infest them with stuff that would infest anyone happening to land there.

Through my experience with both programs I have found Avast to be much superior to Avira. Avast may use a bit more resources, but [at least] it doesn't plant a tracking cookie on your computer with an extremely annoying splash screen (that can NOT be disabled) every time you boot up like Avira does. Avast is a much stronger and more multi-faceted solution than Avira because it is designed to look in more targeted areas of the computer with much stronger heuristics. It also updates in more frequent intervals. I have it set to update every four hours, though it can be set to do so more frequently if desired. In addition, Avast is much more customizable to fit the particular needs of the user whereas Avira uses a more generic shotgun approach.

ONE stinking link does absolutely nothing to prove anything one way or the other. I suppose you believe everything you see advertised in just ONE place and fail to investigate any further, eh? Confused

As for one possible solution to the original question, I have always preferred to use one on-board AV program and back it up with an on-line scanner so that benefit is derived not only from two separate virii databases, but so that if the machine gets infested with something which disables its on-board arsenal, the on-line scan should most likely (at very least) find the problem and either fix it or show me where to look to do it manually. In addition to the on-board and on-line AV solutions, two different anti-spyware solutions, a file shredder (which is used to overwrite the infection's files permanently) and a third party software firewall are included in the anti-malware arsenal and physically wired behind a fire walled router. I have found this to be quite effective! Grin

The infestation I experienced the other day [while in a chat room for the first time in over a year] was the only one I've had since I quit using AVG. Avast cried and disallowed enough of the thing that I could manually finish the job. What Avast couldn't show me, Spybot Search & Destroy did. Because of the fact that these two programs look for different types of files, one backed up the other. This made what could have been a catastrophic instance requiring a week to rebuild the system into a mere two hour job of researching, finding and Erasing the rest of the files contained in the infestation that anti-malware progs alone could not. After finding and cleaning the files I needed to do manually I ran the F-Secure on-line scanner I gave above and it came out squeaky clean! Cool

In addition to computer programs, I use "best practices" by disabling on-board e-mail apps and using web-based e-mail only-NOT even opening spam before simply deleting it, NOT downloading files of any kind except for the few downloadable programs I use, being careful of where I go on the net while doing my research, etc., etc., etc. ..............

If you get right down to it, my laptop running PCLinuxOS 2007 (which I'm writing this from at the present moment) is much more secure than my desktop which has Win XP installed! Wink This is because Windoze is an extremely large target for nefarious miscreants simply because M$ has flooded the market with its "product! This leaves Linux to go on its merry way. LaughMischiefLaugh ...For the time being, that is. Wink

NOW, does THAT "actually answer the guy's question about running two anti-virus apps at the same time" good enough for you? Confused I sincerely hope so. Happy

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just the facts mam
by trojan destroyer / September 23, 2008 9:40 AM PDT
In reply to: Avast or Avira

First off MATE get your facts straight, i didnt malign any 1, if you actually take the time to peruse my comment you will find that with the insertion of a LOL, the entire thrust of my comment was lighthearted and not intentionally used to upset any 1, and going over your POST again and again, any intelligent person will see that you DID NOT ACTUALLY ANSWER THE GUYS QUESTION, the original question was regarding whether 2 and i repeat 2 antivirus apps can be installed and run AT THE SAME TIME, not whether or how many different applications you have tried on your system and found 1 product to be better then the other

And yes i have extensive experience with ALL of the commercially available antivirus and antispyware apps out there, having tested norton, kaspersky, avira, avast, avg, f-secure, sophos, bit defender,mcafee, microworlds e-scan, nod32, norman, spybot search and destroy, superantispyware, malwarebytes, etc as just a sample, on deliberately infected machines which my job reqiuires as im an independent software tester for a major malware research company Happy

Not that i have to justify myself to an obvious Avast fanboy, tech wannabe like yourself i will point out to you that its not just 1 "stinking link" thankyou...........heres another 1 http://www.av-comparatives.org/, you might want to check that out and be embarresed that Avast rates as a mediocre "standard" compared to Avira which scores an "advanced plus" in its detection and abilities as a far superior antivirus application, like i said you might want to check THE FACTS out first before you reply in future to posts....The very fact that you mention that you got infected while using Avast, lol, and that the excellent product Sybot search and destroy had to "finish the job" really goes to show how well Avast is protecting you, hehe, what a joke, Avira would have proactively stopped you getting infected in the first place because of its proven in the wild detection of new or old trojans and viruses that at the moment is far superior to any product in the market out there AND THAT IS A FACT, I would rather put up with an "annoying" ad served by their company and KNOW that i am completely safe as i serf the net

And no, i do not have any loyalty to Avira over avast or any other antivirus app out there as i clean customers computers for a living and actually dont rely on antivirus products per se to aid me, us "professionals" know that in order to do a thorough job you have to root them out of the registry and deregister the viruses and trojans DLL files for any hope of a successful clean

Finally! this simple question rightly deserves a very simple answer...NO!! NO!! YOU CANT AND SHOULDNT HAVE INSTALLED 2 ANTIVIRUS APPICATIONS ON YOUR MACHINE, SIMPLE AS THAT, END OF STORY, END OF POST, if you want a second opinion UNINSTALL FIRST your existing antivirus app first, and then and only then install another antivirus product.....us "real" techies know that antivirus apps install at the kernal level so they have services and drivers running even when you disable them and thats where the system slowdowns and conflicts arise...best advice ONLY HAVE 1 ANTIVRUS INSTALLED AT,A TIME, AS MUCH ANTISPYWARE APPLICATIONS AS YOU WANT, AND THE OCCASSIONAL ON LINE SCAN IS FINE

hope this helps analyzerbunny, and trust GEO2003 what he had to say as well and youre be right Happy

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what i run with no probs ever.
by wayne561965 / September 30, 2008 11:57 PM PDT
In reply to: just the facts mam

well i run norton 2007 internet security and system mechanic 7 and i use privacy guard and spyware doctor and agv all together with never a single problem all actively running together.
so from my piont i can see any problems at all to be honest i just think it depends what your computor is like to certain programs and how they all react together.
so far i have just been lucky you might say but all the same i get loads of alerts from them all and each on does its job correctly as i run another program then the same again to see if its removed and always seem successfull removing things when they appear unexpectedly.

anyway thats me done about what i run on my pc thanks folks.

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by trojan destroyer / October 1, 2008 7:10 AM PDT

Well, well, you are running at the same time norton antivirus 2007 which is a well known system hog, system mechanic 7, which apparently uses the kaspersky antivirus engine,and which DOES slow your computer down, and is so buggy that they had to release system mechanic 8, and avg antivirus, and spyware doctor, i presume youre talking about the 5.5 version, and yet you have encountered NO problems?......your computer must be a hextuplet core running at 10 terahertz overclocked, with 24 gigs of ram,with a 5 terabyte raptor hard drive running at 25000 rpm, and a nvidia geforce 99999 with 30 gigs dedicated vram memory, with 1000 stream processors, shadow clock speed 50 gigahertz with liquid nitrogen super coolers on board, lol

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by DADSGETNDOWN / October 4, 2008 8:24 PM PDT
In reply to: huh?

You should research WAY more than 1 website.
There's alot more than just detection rate to consider also.
Not saying it's bad...

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Only One Anti-Virus
by hogndog / September 22, 2008 7:26 AM PDT

I've heard enough stories to convince me all that you need is one anti-virus appliication, my choice is Avira its both light weight and quite effective with automatic updates + its free. Anti-spyware I use two applications SAS and A-Squared. And to top it off a Comodo Firewall + Comodo's Memory Firewall, all free! I see another poster bring his issue about two anti-virus applications is 100% correct, they will become confused and take it out on you computer.


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Two anti-virus program in one PC
by atshwa / September 22, 2008 9:02 AM PDT

I have installed both AVG and Avast on one PC for years. It works well.
I also help friends installed both program. No problem!

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Can you really have 2 AV programs on one computer?
by drbooth / September 22, 2008 10:56 AM PDT

That is a fairly simple question and deserves a simple answer. No.
It is commonly known that it is not good practice to have two AV programs running on one computer....

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No....The better way is here...
by yoeyar / September 22, 2008 12:07 PM PDT

Dun install two AVs......
1) Avast! AV
2) Spyware terminator
3) COMODO Firewall.
4) Adware as a backup.

That's perfect!!
But both Spy Ter and COMODO will make U troublesome....
U will see how they work....
All are free.


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Generally, NO.
by Tarq57 / September 22, 2008 12:56 PM PDT

As stated above, the AV's install at the kernel level, and even when inactive, still have services and drivers running, which can and do interfere with another AV.
As AV's become more advanced - and they have, particularly recently - they are more likely to conflict with each other. What I'm saying is that what folk might have gotten away with a year or two ago doesn't necessarily apply now.
You might get away with it, you might not. If you don't, the first clue might be when the two AV's lock up should real malware be detected. Not a good time to have a locked up computer.
A better solution is to have one AV installed. Avast is good. Avira is good. NOD32 is good. AVG...some folk like it.
When you want a second opinion, do an online scan (many available, as indicated in answer#1) or download and run the standalone DrWeb Cureit scanner, which is very good. Just pause the realtime shield of your resident AV while running it.

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Did it for years, works well for me
by FatCatPeter / September 22, 2008 3:56 PM PDT

I have no machine where I depend on one manufacturer claiming that just one product can offer full protection. Look at the tests, there is no such thing as 100% detection/protection.

Let me put it like this - ever since we had been hit by a zero-day attack some years ago, we have been using several anti-(virus/spy...) programs on the same machines. Even though we were protected by the anti-virus scanner of a VPN and a scanner running on the local machines, the bug hit us - simply because both scanners were updated _after_ we had been hit. We used a third application to catch the bug; obviously the updating schedule of that application was more effective.

Another aspect that you might want to take into consideration is that none of these applications catches all bugs. So, as they work differently, chances are that the bug not caught by application A might be caught by application B (which has been the case on some of our machines).

Even running a scan with, let's say Adaware or Spybot Search & Destroy, might trigger a bug to be caught that (strange enough) could not be detected by the very anti-virus application when doing a full scan before.
Looks like one way to probe files lets a certain bug jump, other ways are not effective for this bug but might be for others.

Last not least the question of stability and speed. Depends on what you use your machine for. Usually the machines are overpowered for office use, anyway. So a certain slowdown by the constant scanning does not really matter. If you feel you need more speed - switch some stuff off (but not all).
Stability - well, it is a no-brainer:
- Machine runs stable even with half a dozen of protective applications guarding your machine - great. You can't have enough protection!
- Machine gets quirky - just spend a little time to identify the conflicting application(s) and switch it/them of. Or just use one (as suggested in other replies), so nothing lost Wink

We have been doing this for years now and from my experience speaking, compatibility and/or stability seems to be more a matter of hardware components than a matter of several protective applications running at the same time.

On my private machines (desktops and laptop) the following is running in memory: AVG and Avira (anti-virus), Spyware Doctor (Google pack version), and the Tea Timer of Spybot Search & Destroy (does report attempts to change the registry). Works well for me.

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you make good point fatcatpeter
by wayne561965 / October 2, 2008 7:07 AM PDT

at last someone who feels exactly as i do and runs a pc like i do and has some really valid points made here too.
well said my friend.

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Firewall, Anti-Virus verses Anti-Spyware/Anti-Adware
by CKinVA / October 15, 2008 2:19 AM PDT

One needs to keep in mind the difference between products. Generally:

1. Firewall products monitor communications ports ... They must run at (are hooked into) the operating system level.

2. Anti-Virus products monitor a lot of things: File reads/writes, Software installs, E-Mail activity/attachments, Registry changes, Some network activity, Browser add-on install attempts, etc ... To provide 'real-time' protection they must also run at (hooked into) the operating system level, however they do not need to do so just to do an 'on-demand' scan of your system.

3. Anti-Spyware/Anti-Adware tend to look for attempts to access or execute known 'bad' program files, etc ... they are almost always run on-demand thus you may have multiple products installed as they will be self-contained in their own directory (not in the operating systems directory); however, some products offer real-time protection (IE: SpyBot S & D "TeaTimer") and the 'real-time' functions must be run at (hooked into) the OS also.

Each of these toolsets may 'modify' specific parts of the operating system by replacing the operating systems default program with their own (ie: inserting the 'hook') ... I say MAY because obviously a product designed to be manually fired up from an on-line site or the local C: drive usually does not modify the OS, but those products that 'run in the background' (ie: are started when you boot the PC) typically do hook into OS files.

Given this:
4) If you install multiple products that are designed to 'stay within their world' (ie: a firewall product that does not include a built in anti-virus tool and an anti-virus tool that does not include a firewall) you will be OK; however,
5) if you install multiple products that: a) hook into the OS, and b) overlap in function (ie: 2 anti-virus checkers) they may overlay each others 'hooks' in the OS and you may not be OK.
6) keep in mind that every product installed will also modify the system registry (often used by the OS to find the program to be executed for a specific function), reconfiguring it to 'point' to that products executables when a certain condition occurs (ie: an 'open .exe file') ... thus the 'registry hooks' can also be reconfigured multiple times.

Additionally, should you install 2 anti-virus products, when you uninstall one of them, you may really be left with a mix of program files & registry entries that may trash your system effectively.

Note: due to anti-trust laws, etc., the Microsoft defender/firewall tools can 'exist' with other products; however, you should configure your system to have the Microsoft products disabled or you may run into problems and/or have horrible response issues.

I say this based upon working over 40 years as an IT specialist.

Goodtime Charlie, VA

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