I have tried and used several anti-virus suites of software. I would have no problem recommending any of the following: AVG, Avast, Panda Cloud, Avira, and Microsoft Security Essentials.
Of course, things get more difficult when a nasty virus/malware slips thru and disables your anti-virus.
My go to program is Malwarebytes' Anti-Malware Free. I install this on any computer I sit down and work on. Awesome tool and is the first thing I use to try and remove malware. If you don't have any luck with it, be sure to try using it in Safe Mode (with networking).
8 out of 10 times, Malwarebytes solves the problem. But ocasionally it doesn't get everything. I have found Combofix to be my next weapon. It is a little intimidating (and very powerful). But follow the directions and it will work.
I cam across some other anti-malware that I haven't' used before (but will):
emisisoft emergency kit 2.o
Norman Malware Cleaner 2.1
Norton Power Eraser