Windows Defender detects and removes spyware
Windows Defender is software that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software by detecting and removing known spyware from your computer. Windows Defender features Real-Time Protection, a monitoring system that recommends actions against spyware when it's detected, minimizes interruptions, and helps you stay productive.
http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
...
SuperAntiSpyware
SUPERAntiSpyware is the most thorough AntiSpyware scanner on the market. Our Multi-Dimensional Scanning and Process Interrogation Technology will detect spyware that other products miss! SUPERAntiSpyware will remove ALL the Spyware, NOT just the easy ones!
http://www.superantispyware.com/
......
Malwarebytes' Anti-Malware
Malwarebytes' Anti-Malware is considered to be the next step in the detection and removal of malware. We compiled a number of new technologies that are designed to quickly detect, destroy, and prevent malware. Malwarebytes' Anti-Malware can detect and remove malware that even the most well-known Anti-Virus and Anti-Malware applications on the market today cannot. Malwarebytes' Anti-Malware monitors every process and stops malicious processes before they even start.
MY favourites are MBAM AND SAS 
As the free versions don't have "real time", you can have more than 1 Anti Malware scanner on your computer.
Hello
Does Super Anti Spyware (free edition) do the same job as Windows Defender?
Should I use one or the other - or both on the same computer.
I run an XP and a Vista machine and would appreciate advice to protect both computers.
Thank you
Steve
Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic