No. In my experience, for all the free shit you can get for your computer, just pay the price for good anti-virus software. For me it's Nortons, but go with what you like.
If you have annoying viruses that don't seem to go away start your pc in safe mode with networking (so you can still access the net) and go online and download spybot search and destroy (free) here http://fileforum.betanews.com/detail/Spybot-Search-Destroy/1043809773/1 and hitman pro (free trial) here http://www.surfright.nl/en and run them immediately. They should find most things and when you restart your pc as normal there should be no problems anymore.