Currently I'm using Avast for anti-virus protection. Prior to that I used ZoneAlarm for a year, and prior to that I used Kaspersky's for a year.
I honestly don't remember if ZA or K ever found a virus during a routine scan. I do know that they prevented me from downloading infected files in the first place and that they wouldn't let me go to Web pages they determined to be unsafe.
One downside to the free version of Avast is that you can't schedule automatic scans, you have to initiate scans manually. I'll admit that I'm probably not scanning as often as I should. I ran a scan last night and found 5 infected files. That's a bit troubling.
After seeing Mitchy's post, I decided to get Malwarebytes and to run Eset's free online scan as suggested by msmooooth. Malwarebytes didn't find anything, but I haven't yet run a full scan, only a quick scan. Eset found another virus, win32/induc.a, which seems to have hit in just the past couple of days.
I updated all my anti-virus and spyware programs and have been running scans. Nothing else has popped up yet. But it's weird that I should find so many infected files in a 2-day period when I never really had problems with viruses or spyware before now. I think over the next few days I'll run more frequent updates & scans just to see if anything else pops up. I may also try another free online virus scan, since Eset's online scanner found something the other programs missed.