As multiple people have put up.. AVG (same as www.grisoft.com) is the way to go. Automatic updating and scheduling, pretty up to date and seems to catch about everything. I've run it up against Norton and Mcafee and haven't had either of them catch anything AVG missed.
Just to chime in, I've been using Grisoft's AVG for years, and it's been excellent and easy to use. Also, about once a week I go to Trend Micro's site and run their free online scanner. Can't be too careful.