Microsoft now has a malicious software removal tool that is able to remove the most virulent worms and viruses. The tool is updated once a month and is part of Microsoft's scheduled software patch cycle.
The initial version of the tool was able to detect and remove Blaster, Sasser, MyDoom, DoomJuice, Zindos, Berweb/Download.Ject, Gailbot and Nachi viruses. The tool will be downloaded and run automatically if your computer has 'Automatic Updates' enabled. It can also be executed manually from Microsoft's site as an ActiveX control in the Internet Explorer browser. You can also download the tool from Microsoft's Download Center.
For more information, see the following MSKB 890830 ("The Microsoft Windows Malicious Software Removal Tool helps remove specific, prevalent malicious software from computers that are running Windows Server 2003, Windows XP, or Windows 2000")