I am currently running "F-Secure" as my anti-flu medication.. linked from the windows updater. It gives you six months free trial.
Barely noitice it most times.. But when i' going through the router (so the kid can get online on his puter too) , I do notice that it takes longer to decide if somethings bad or not..

I will say that it found lots of stuff that norton never noticed.. or spyware for that matter..

I have lime-pro as well.. Not a virus yet.. just stupid page poppers from vids that i download..