Microsoft released the Microsoft Windows Malicious Software Removal Tool to help remove specific prevalent malicious software from computers that are running Windows Vista, Windows Server 2003, Windows Server 2008, Windows XP, or Windows 2000. After you download the Microsoft Malicious Software Removal Tool, it runs one time to check your computer for inflection by specific prevalent malicious software (including Blaster, Sasser, and Mydoom) and helps remove any infection it finds. Microsoft releases a new version of the tool every month.
You can download the tool from here.
For more information , see knowledge base article KB890830
For Microsoft Security Bulletin Summary for July 2009, go to this site.