Okay, just to address a few things; AVG IMO is crapware, that's why I listed it. Not 'cause it's a resource hog.
NOD32 is the antiviral suite I'd use, IF I ever used one. When I load up someone else's PC, that's what I use. It's #1. Period.
OneCare is junk, as it is just an AV bought from someone and rebranded and integrated so MS could pass it off as its own. It fails almost all AV tests, just so you guys know (And it also causes a lot of problems with newbs, locking them out of the internet and such)