Free antivirus programs...

With my recent upgrade to XP Pro I need a new AV program. I know there's a bunch of different free ones, but I don't know which one to try, if any. I'm looking for something that gets updated regularly and will work in XP (obviously). Anyone have any experiences with any of these? I've looked at AVG AntiVirus and AntiVir. Or is anyone here running XP with Norton AV 2000? I have a copy that a friend gave me but am afraid to try it since it came out before XP. NAV2003 looks pretty good, but I'd rather not buy it if I can get a good one for free. I don't need a lot of bells and whistles, just the ability to scan files by right clicking on them--that kinda thing. Any ideas?
I can heartily recommend Computer Associates' ezTrust Antivirus. Small, fast, daily updates and offers file scanning (on-access and on-demand) and NOTHING else. Not free, but good value at $19.95 per year.