I'll need to do a little more research, but a quick search of my Win XP I found the following:
Spybot - Search & Destroy
Malwarebytes’ Anti-Malware

I think there was one I uninstalled because it clashed with another one, gave a message it could not run whilst the other was installed. Some kind of anti-competition code I was guessing.

There might have also been another I uninstalled after it finished doing its job.

I cannot do the research at the moment, I have a full day but will do it this evening.

Edit: A quick search and I found I mentioned having tried these:
Malwarebytes' Anti-Malware, Spybot, SpywareBlaster, Ad-Aware, SuperAntiSpyware, Malicious Software Removal Tool