Are you using the latest version of SpyBot S&D? If not, that's the same as using an out-of-date antivirus application. Make sure you update SpyBot. I use it all the time and it's worked for me. The other one I use is MS AntiSpyware Tool. Yeah, I know....but I wouldn't use it if it didn't do its job. It actually picks up things that SpyBot might have missed on the first go-round. Unfortunately, MS AntiSpyware requires Windows 2000 and above. SpyBot will install on on any Windows.
BTW, the actual SpyBot S&D site is
http://www.safer-networking.net. If you do the ".com" at the end you wil be sent to a site that is actually a spyware site. Bastids!
Anyways, once you install it you might want to go ahead in "Safe Mode with Networking" and run it so that no applications startup automatically after reaching the desktop. That's worked for me in the past with SpyBot and MS's app.