When the free trial of the security software that shipped with my Vista PC expired, I decided to uninstall it and give the free versions of competing antivirus and firewall programs a try. For some reason, this caused my Internet connection to drop intermittently.
When I uninstalled the new programs and ponied up for the full version of the security suite, the network outages ceased. I never did figure out why my system didn't take to the new security apps, but the hassles I avoided by taking the suite approach to security justified the cost of the program.
The experience got me thinking about whether I need any antivirus software at all. I've got athat saves my data files regularly, and I don't usually frequent the Internet's dicier locations.
Ultimately, I decided that security software is really PC insurance. Even careful, cautious, tech-savvy people can fall prey to a malware attack. It would take only one thwarted infection for the program to prove its worth. And sticking with a single security vendor whose products are proven effective is the best way I know to reduce the chances of compatibility problems.
In PC World's most recent review of security suites, Symantec's $70 Norton Internet Security finished a couple of notches above the $80 Kaspersky Internet Security and $70 McAfee Internet Security Suite.
Sometimes it's okay to put down your defenses
Most security programs have some components that are always active. This robs your system some processing power and memory. Just how much processing power and memory depends on the program and how it's configured.
When you're running an application that requires all the system resources your PC can muster, you can reclaim a few by temporarily closing your antivirus program. The fastest way to do this may be to right-click its icon in the system tray and choose Exit or Close. It's a good idea to keep your firewall running at all times, but if none of your open apps have an Internet link active, you can do without virus protection.
If your browser fails to open certain sites or your network link starts acting up in some other way, a short-term solution may be to shut down your security program temporarily. (You can also try.) If closing the security app restores the network connection, add the balky sites to the program's white list of safe Web destinations.
Wikipedia's antivirus page provides loads of background on the programs. Of particular interest are the page's "Issues of concern" and "Effectiveness" sections (scroll down to find them).