Eventhough mcafee and norton eats your computer's resources I think there's a lot of things that you can get from the two antivir mentioned compared to those free ones on the net plus your guaranteed there's no adware or spyware that will be installed on your system(who knows everything being downloaded on the net seems to have a spyware or adware attached to it and sends your computer info to whoever owns it, in general)... well that's my opinion though... but for free one's I can suggest the latest AVG(free edition, latest) paired with Ad-ware 6.0 works great but it won't heal some of the trojan/worms but at the very least it will detect it and you can find a way to irraticate the criters before it spreads out on your machine...
