Microsoft officially announced its plans to field a Microsoft-branded anti-spyware product (code-named "Atlanta") in January, following its purchase of Giant Software in December, 2004.
The anti-spyware beta supports Windows 2000, Windows XP and Windows Server 2003.
Microsoft released the first beta (Build number 1.0.501) of Windows AntiSpyware on January 6.
Since then, the company has made available regular beta refreshes of the product.
In June, Microsoft released an interim beta refresh at the same time as it extended the Windows AntiSpyware beta expiration date to December 31, 2005.