Free AntiSpyware Programs

Ad-Aware 2007 Free
Ad-Aware is a free antispyware for Windows (including Vista-32bit) systems.
It removes Trojan horses worms,spyware and backdoors.
It can repair the damages caused by a malware.
Download Page
---------------------------------------------------------------------------------------

Bazooka™ Adware and Spyware Scanner
Bazooka detects 500+ spywares, adwares, keyloggers, dialers and other malwares.
Bazooka™ is free and Windows 95/98/ME/NT/2000/XP compatible.
Download Page
-------------------------------------------------------------------------------------

HijackThis
HijackThis V2 analyzes certain key parts of the Registry and Hard Drive and lists their contents.If you have run any other spyware removal software (Ad-aware, AVG Antispyware, SuperAntiSpyware), please restart before scanning.
Download link is on the same above page.
Statutory warning: Changing the registry files by yourself(not by HijackThis) can affect your system.
------------------------------------------------------------------------------------

Spybot - Search & Destroy
Spybot - Search & Destroy detects spyware/malvare in your system. It is Vista compatible.
Download page