I'm using McAfee and mine expires shortly.  Kevy (and other LoTers) have pointed me to 
AVG free.  I like it, and I am actually not going to renew McAfee and go with the full $50 pay version of AVG.  For one thing, when it scans my PC, it does not slow it down, which is a good thing.
Oh, the only downside to the free version of AVG is that it does scan your PC every day, you can't schedule it to scan weekly.  It's not a big deal, I merely cancel the scan.  It updates daily and runs great.