Microsoft released its final version of Windows Defender on Tuesday (Formerly known as Microsoft Antispyware). The last release was beta 2 in February. Since then about 30 million people have downloaded it.
It is a well polished product, and so far it has been great at removing most of the spyware that I have encountered. Now that it is an official full product, and no longer beta I am concerned that it could demolish other anti-spyware vendors like Ad-Aware and SpyBot
If it comes down to only Microsoft as an anti-spyware vendor I feel that we will be back to square one. This is because the spammers, and spyware creators out there will only have one simple target to hit.
In addition to the software being free, Windows 2003 and XP users are entitled to two free support calls for Defender.
Not surprising, but the Defender is included with the Microsoft AntiVirus product Windows One Care. Now you can see why they want to lock out other vendors 
Download Windows Defender Here
Other excellent anti-spyware tools can be found here: