Honeslty, it's all about safe surfing habits. I have not ran an antivirus program on any of my PCs (five at last count for personal use) in at least three years. About once a year, I install and update ComboFix and MBAM and run them just to check; they never find a thing, so I uninstall them.
Just remember:
If it says it's free, it usually isn't.
If it claims to help, it probably won't.
If it offers you great porn, it's probably goatse.