Sophos is a very good antivirus. I use Kaspersky Lite for $19.95. The program doesn't have all the bells and whistles such as ability to select folders to scan, and it doesn't update automatically. Kaspersky does provide daily updates, or you can update the whole package on a weekly basis.

http://www.kaspersky.com

One of the top AV's seems to be NOD32, if you can afford the $54.95 price. The downside, from what I've heard, is that it's a pretty technical setup. I don't have the URL available.

For free, AVG and Antivir both seem to be good. For some reason Antivir won't do a full scan on my machine. It freezes about halfway. Another freeware is AVAST32 which I've heard good things about. I tried it and it seemed to work fine. I got Antivir and AVAST from http://www.webattack.com, their freeware section.

For me, I just have more faith in Kaspersky, especially the fact that they provide updates every day as new viruses are found.