I've been using Zone Alarm free and AVG for a while now. I think for the most part common sense can keep your PC safe. In any case, malware always seems to make it into your PC.
I only read the first post in the topic, so bare with me. I personally use Ubuntu as my main O/S, so I really don't need an Anti-Virus. However, if you feel the need to stick with Windows, I strongly suggest "Spyware Doctor With Anti-Virus".
Im using right now Trend Micro Internet Security 2008 and it works very well for me.. It really blocks virus... But the downside here is that this anti virus can't be installed to older models of laptops and pcs..
I use NOD32 that is ESET SMART SECURITY that is really cool but i am thinking of changing the package to a new local company in India its called quick heal and my friends are giving great reviews for their product so I am willing try their product best of all their price is around $7 for a year which is awesome