Spyware Doctor has pulled my buns out of the fire more times than I can count. It's also an effective defense against those evil hidden rootkits, or any memory resident program, whether it's running or not.  That should include keyloggers.
You can download the demo for free to give it a test run, but you'll have to pay for a fully functional version. So it goes.

http://www.pctools.com/spyware-doctor/

AVG Free Edition has performed better for me than any other commercial AV program. If you're a Firefox user, there's a plugin that will identify dangerous sites when doing doing a URL search on any search engine.

http://download.cnet.com/AVG-Anti-Virus-Free-Edition/3000-2239_4-10320142.html

Since I've been using these two apps together, I've never had any sort of infected file problems.