After nearly two years in beta testing, Microsoft has at long last released the final version of Windows Defender, its free anti-spyware software. The tool is available now for Windows XP, and will ship as part of Windows Vista.

Originally named Windows AntiSpyware, Defender came from Microsoft's acquisition of GIANT Software. The company bulked up the detection engine and added protection for pop-ups and other malware that affects PC performance. By offering Windows Defender without cost, however, Microsoft has irked some security vendors.

The final Windows Defender release -- build number 1592 -- brings a number of minor improvements to the software including IE7 integration and interface tweaks. Beta 2 previously introduced a new "Real Time Protection" engine that monitors critical areas of the operating system for any changes, as well as accessibility enhancements.

Microsoft has also added support for 64-bit versions of Windows XP and Windows Server 2003. But support for Windows 2000 has been dropped, as the operating system is now out of mainstream support. The Redmond company is offering customers two free support incidents for the software.

Windows Defender is available for download for both 32-bit versions of Windows and x64 editions. The software requires Windows Genuine Advantage verification to use.

 Download: Windows Defender 1592