I've also found NOD32 lightweight, fast, and reliable. It also always gets very good scores in independent tests. The other one's that's light on system resources but very effective is Kaspersky. And if funds are tight Grisoft's AVG is free to home users.
But no way will I use anything from Symantec or McAfee. I've read that the Norton corporate AV product is good. The same can't be said for the home version. They got in a features war with McAfee and both "security suites" do far more than anyone needs and do it badly. In addition, Norton internet Security is a pig to uninstall - just look what you have to go through to get it off a system:
http://www.askdavetaylor.com/how_to_fully_remove_norton_from_pc.html
No way should that sort of nonsense be necessary.