Best Free Spyware & Adware Remover

The first is Microsoft's Windows Defender program. Defender is the latest re-incarnation of the excellent Giant Antispyware product. Windows Defender is not as effective as its immediate predecessor but still has solid protective capability. I tested it on several drive-by download sites and its multiple real time monitors provided reasonable defense. It appears to be a little vulnerable to polymorphic malware in particular and for this reason I suggest it should be used in combination with regular on-demand scans from the free AVG Anti-Spyware. And other drawback about Windows Defender is that it consumes quite a lot of your processing power. If you have a modern PC this should not be a problem but older machines will definitely suffer a performance hit. Note that you need a legal version of Windows XP SP2 to run this program.

http://www.microsoft.com/downloads/details.aspx?FamilyID=435bfce7-da2b-4a6a-afa4-f7f14e605a0d&displaylang=en

So my recommandation is Spyware Terminator. Unlike Windows Defender it works with all versions of Windows so it's the stand-out choice for Windows 9x users. Like Windows Defender it has strong active protection. Indeed with its built in HIPS system that warns you of any unrecognized intruders, it has stronger protection against unknown threats than the Microsoft product. This was confirmed on some tests I ran on drive-by download sites where Spyware Terminator proved to be impregnable.
Spyware Terminator has it's own spyware detection engine but gives you the option of using a second engine based on the Open Source ClamWin anti-virus program. ClamAV is not the most effective AV scanner on the market but it's certainly competent and the additional protection can only be a plus.
On the downside Spyware Terminator is slow to scan and can slow down your PC a tad though not as much as Windows Defender. I've also heard reports that support via the free forum is poor.
Choosing between Windows Defender and Spyware Terminator is not easy. As of today I think Spyware Terminator has the edge but it's difficult to see how free product like this can remain viable, particularly in a high support product class such as anti-spyware.
http://www.spywareterminator.com/