Malicious Software Removal Tool from Microsoft

The Microsoft Windows Malicious Software Removal Tool checks computers running Windows XP, Windows 2000, and Windows Server 2003 for infections by specific, prevalent malicious software including Blaster, Sasser, and Mydoom and helps remove any infection found. When the detection and removal process is complete, the tool displays a report describing the outcome, including which, if any, malicious software was detected and removed.

Link: http://www.microsoft.com/security/malwareremove/default.mspx