Regret to disagree about McAfee. I was a long term fan and used McAfee's Viruscan and Internet security suite for ages but just have had too much trouble with it's later incarnations.
And Viruscan 8 seems fraught with "problems" (see
http://forums.mcafeehelp.com/ ) - I moved to Norton and a hardware firewall (FreeSCO router) and haven't regretted it.
Norton AV and ZoneAlarm Pro is probably the best combo for a single PC setup.