To clean my computer I use:
Ad-Aware --
http://www.lavasoftusa.com/software/adaware/SpyBot S&D --
http://www.safer-networking.org/en/index.htmlThese are both free programs and aren't scams like many other spyware cleaners(which often install their own spyware/adware while pretending to be a good program and cleaning other companies stuff off your comp). They might even be better than other pay programs.
I also use SpywareBlaster to configure my ActiveX and restrict bad sites
(
http://www.javacoolsoftware.com/spywareblaster.html)
It's also free and doesn't run in the background to protect spyware from getting on your computer. (This also has integrated FireFox protection)
Finally Microsoft offers a compound scanner/real time protection in its MicroSoft AntiSpyware program. It's still in Beta but does work great, I didn't keep it because I feel my other programs clean/protect better and don't run in the background. This is also available for free at:
http://www.microsoft.com/athome/security/spyware/software/default.mspx .