I have a dual boot system using win98&winxp. In winxp I used at first Norton av 2002 but after a lot of troubles I had to change. I look here and choose one of the recomended AV, in this moment were F-Secure, AVG and PC-Cillin 2002 v9.02. I decided for PC-Cillin becouse it scan all incaming POP3 mail. But the story is a "neverend story", becouse I install a PCI network Ethernet card to connect an ADSL modem. Under win98 no problem at all, PC-Cillin goon working great, but under winxp the realtime monitor didn't start when windows start. So I decide to test other XP compatibles antivirus, and I search for those that scann email. I test panda antivirus titanium but didn't like it to much, to simple, you can't configure anything, I test panda platinum, it's seems to be more complet but you need a registrated username and password to update antivirus definitions. I test Kasper antivirus but I found it very slowly. At this point I decide to use F-Secure 5.40. I found it terrible fast if you compare with previous versions and with the other antivirus mentioned above (except PC-Cillin), the autoupdate antivirus options works great, and I surprised to see that the updates are practically every day. I don't like that it doesn't scan mail, but the real time monitor works great, so If a virus is send by mail you have to delete it manually (the antivirus delete from the temp directory when you open the atached virusfile but don delete the atach itself). I would have to test AVG to get a complet evaluation of the recomended AV, I promisse I'll do next time I have to reinstall xp.
I read about NOD32 is a great if not the best antivirus but same problem of panda platinum, without being a registrated user no liveupdate available.