Being the pessimist that I am, and my ISP once providing 'free' anti-virus... be wary. No such thing as a free lunch and they might, down the road in a few months, start charging you $5 a month for the free anti-virus like my ISP did a while back. (No longer with them).
The Free AVG is okay, but it seems to detect but not remove viruses. Removal is a more manual process from my experiences with it.
Another thought on AV protection is, eSet NOD32. Not a resource hog does a good job at virus and malware removal. Updates come out more than once a day when the need arises where Norton (Symantec) might do it just once a day. Symantec just let too much through and is, IMHO poor on spyware and other malware. Based in the center of the viri and malware arena (Slovakia) seems they get a good jump on new stuff coming out. Kaspersky is good also, but for my company we didn't buy because he used to be a KGB agent (factual), a Russian company and who knows what's in his code.
My .02 cents anyway for whatever it is worth. Lots to choose from.