IMO, this would be the best thing to do.

Completely Wipe your hard drive.
Reinstall Windows. (NTFS of course)
Get all the updates available. And i Mean all of them.
Then get your drivers installed.
Turn on XP Firewall, screw 3rd Party AV software.
Youll be alright from there.

I havent used AV software since 2003. I noticed that AVs just slow down my computer, and just having common sense on the internet and having XPs firewall turned on, works just fine,