Well this depends upon more than just software.
There are several things to consider.
1. Are you behind a hardware firewall?
2. Software saavy or not?
3. Processing speed, & memory
4. How much time do you have to attend to the scans?
5. What types of sites do you surf, what are your downloading & reading habits, when downloading progs?
If you don't have the time, or saavy, then an all in 1 suite, that auto-updates is probably the best bet.
However if your computer is slow, than most of the all in 1 security suites will really bog your system down.
If you're behind a secure hardware firewall/router, then a software firewall is a lot less imperative, & is a resource hog.
More important is that you have your router security settings turned on WPA-PSK with a strong password that you change monthly...
It's all really very individual...
I've used Avast with great success after uninstalling Norton back in 2003.
A truly good Virus prog..
All you need to do is to register, & you're good for over a year, then you just re-register.
It isn't as good as NOD32, F Secure, AntiVir, & Kaspersky AV, that flat out have the best detection, but it works fine for me.
For spyware i have the paid version Webroot spy sweeper, because it's just flat out the best there is right now.
The real time scanning is second to none IMO..
There isn't really a free product that gives this kind of protection.
Spyware terminator, & windows defender do an ok job, but i'd rather pay the few bucks to feel more secure.
Also be sure to do a scan for rootkits.. Wiki the term for a thorough explanation, as it is a newer class of malicious crap to look out for lol, then head to techsupportalert dotcom to read reviews on some of the free removal products out there.
"Rootkits are a special kind of software tool used to hide trojans, viruses and other malware from your anti virus scanner and other security products. Unfortunately, they are extremely effective which means that some of you reading this will be infected even though you believe your PC to be totally clean."
From Gizmo's site.. I def recommend what he says below..
"If you use Windows 2000 or later my top recommendation for safe browsing is a free program called Sandboxie that creates a special contained "sandbox" environment on your PC. While browsing within the virtual sandbox provided by Sandboxie you are totally corralled off from other parts of your PC. So any files you download are isolated to the sandbox. Similarly, any programs that are executed only do so within the sandbox and have no access to your normal files, the Windows operating system or any other part of your PC.
Usage is remarkably simple. To start a sandboxed browsing session you just click the Sandboxie icon from the Quick Launch tray and this will launch your default browser in the sandbox. You can then use it in the normal way to browse to sites or download files.
If you download a file it will install normally but again will be corralled off from your real PC as any new processes running in your computer memory or entries in the Windows startup areas will be sandboxed.
After you have finished browsing you can right click the Sandboxie icon and delete all sandboxed files and processes and your PC will be returned to much the same state it was in before the browsing session. If you want retain particular downloaded files you can save them permanently before clearing the contents of the Sandbox.
The advantage is clear: any spyware, trojans, keyloggers or other malware products that infected your PC while browsing will be eliminated.
Sandboxie works fine with all browsers but requires Windows 2000 and later. It can cause problems on some PCs so backup before installing."