I'm gonna respectfully disagree with MustISO's reply (no offense, of course).
Over the last several years, the anti-spyware test reports in the top computer magazines like CPU, PC Magazine and PC World have had a common result: virtually all anti-spyware apps (particularly the free ones) have difficulty, to one extent or another, detecting keyloggers. I've been reading them for several years, and the two with the best performance against keyloggers over that time have consistently been Spy Sweeper and Spyware Doctor.
The old "freebies" that made names for themselves earlier this decade -- AdAware and Spybot S&D -- are now pretty much considered to be a joke by those who conduct credible tests. Their detection rates are very poor compared to what they once were. I would have zero confidence in a 'clean' scan report from either of those programs. Most sophisticated malware just brushes them aside.
I've had a little personal experience with both SS and SD and like the latter better because it has a feature called "Kernel Compatibility Mode" (which you have to enable) that allows it to engage the OS at the kernel level and thus allow concurrent operation with a separate a-v application without significant system slowdown. My experience with using SS in conjunction with an a-v app is that noticeable slowdown does occur (both apps try to do their real-time monitoring at the same time and conflict with each other).
In your sitch, my personal recommendation would be to install the trial version of Spyware Doctor, run a scan, and then go online and run Microsoft's LiveOneCare Safety Scanner as a second round. Its detection rates were a joke not long ago, but they've improved dramatically. Although anything's possible, it's not highly likely that a common keylogger app will be able to evade both (particularly if it's a commercial one designed for spousal or child monitoring).
'Course, Mech's nuclear option will give the highest certainty of success.