The antispyware software on this page is free. Free software may be the solution to your problem, but sometimes paid software does a better job. I believe this is one of those times.
These programs should be in your spyware arsenal, but you should look to one of the paid programs at My Software Picks as your primary spyware tool.
a-squared free - a free rootkit, spyware, trojan, and malware tool.
AdWare SE - a free adware tool. The paid version is listed in the Dave's Picks section. The paid version offers automatic updates and resident protection.
AVG Anti-Rootkit - a free program to find and remove rootkits.
Ewido - My personal favorite of the free spyware programs. 30 day trial. After 30 days it reverts to "free" mode. No resident protection and no automatic updates are available in free mode. The paid version is listed in the Dave's Picks section. One of my favorites.
GMer - a free program to find and remove rootkits.
HijackThis - a useful tool for diagnosing spyware/malware infestations.
HookExplorer - a small utility to scan a target process and identify any user land hooks that may be installed by unknown code.
IceSword - a free program to find and remove rootkits.
Sophos Anti-Rootkit - a free program to find and remove rootkits.
Spybot - free spyware tool.
SpywareBlaster - free spyware and adware tool. This program adds sites which contain spyware to the blocked sites list of Firefox and Internet Explorer.
Windows Defender - free Microsoft spyware and adware tool. Similar to Ewido, but not as good in my opinion. This software is still in Beta.