I use Avast....free.....never had a problem.....touch wood. I run it in conjunction with the Windows XP Firewall and Prevx1. Oh, and a built in Firewall in a Netgear Router.
I have tried Norton (PC Hungry), Norman (good but vague....doesn't let you access it), McAfee (Horrible), Bullguard (just as horrible).......Horrible means a word that starts with c and ends with p.
Al.