Recommendations for an Anti-Virus program?

I think I'm going to have to remove Avast! from my machine. I've been getting freeze-and-shutdowns on it, and I think it's because Avast! and Zone Alarm don't like each other.

I used to use BitDefender, which I never had any problem with. I might go back to that.

Anyone have any suggestions for a freeware anti-virus program for a Windows machine?