Seriously man, I run Microsoft Security Essentials as my AV, and Malwarebytes as my virus hunter/killer.
I schedule them to scan once a week, and I haven't had a virus problem in 3+ years. That's with watching a respectable (normal) amount of porn.
+1 for MSE. Haven't had a virus fuck me in about 10 years and I download a ton of torrents. If I had unlimited money I would consider a mac but paying 300% more for the same specs is dumb to me unless you work in the creative industry and have to use mac specific software.