Personally, I use microsoft security essentials as my primary antivirus software, and the free version of malwarebytes for occasional scans. Combined, I get fairly decent antivirus protection for free. What are your preferences?
I'm not doctor anti-virus, but I primarily use avast! for my virus protection. It brutally punishes ANY virus that dare threatens my computer toaster
I have the free version of avast, and I like it, but it usually doesn't catch things as fast as malwarebytes. More protection doesn't hurt though
I have McLaffee... it tends to screw things up but has good protection.
Once upon a time I had Norton and ZoneAlarm.
I used to use norton, and it was a major performance drag on my PC. I'm glad I'm not using norton anymore.
For my firewall I just the windows default, which is probably a bad idea.
I am stupid and I just use the Security Essentials from MS. Not that I ever download anything fishy anyway!
I try to avoid downloading fishy stuff, but somehow I always end up with junk on my system. I think half of it is Windows' fault though.