Dunno. It's been a long long time since I had a virus. But I had antivirus just yesterday. It started out virtuously enough. I decided to do a virus check on the laptop. It's been a long time, so each of my antivirus programs updated itself, and its database over the internet. After each update, a lengthy scan. Two hours in one case. I ran my favorite three, Ad-Aware, Spybot Search & Destroy, and AVG. All are freebies available for down loading. No virii were detected by any of the three.
Next morning, I booted up to check email and do some websurfing. Boot was ultra sluggish, and loading Thunderbird took so long I though the machine had crashed. Hitting Ctl-Alt-Del brought up the Windows task manager, which revealed that a "process" named AAWsomething-or-other was hogging as much as 100% of my CPU time. Some hackers had "improved" Ad-Aware to always load a real time scanner at boot time. This baby is supposed to check traffic one the internet and alarm when it sees a virus slipping into your machine. That's nice and all, but it slows the machine down too damn much. So, uninstall AdAware.
Next day, machine is still running slow. Task Manager shows a bunch of "processes" named AVGsomething-or-other are active. Must be real time scanners installed by AVG. So, uninstall AVG.
Today, boot up, and draw a couple of scary error messages at boot time. One message said "Cannot find a file with a name that starts with AVG". So much for a clean uninstall. Then it started Firefox to run a survey from AVG asking why I had uninstalled AVG.
So, now I am running almost barefoot. I still have firewall up (ZoneAlarm) but no realtime scanners and no disc scanners. I don't do file sharing, I don't insert strange media (flash drives, floppy disks or CD's), the router has been doing a good job as firewall, and I have autorun turned off. The desktop has run bare foot and virus free for more than a year. Lets see if laptop is as lucky.