There is a fix for this worm, the details are on our security site at http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx
Please read the above bulletin for the full details, the patches to prevent this worm are on that page.
I am wondering why Microsoft has not created a security update for Window XP SP1? There are vendors that we deal with in the lab environment that won't support thier software or the software doesn't work properly if the operating system is upgraded to SP2 or higher. This is a problem I am facing now with our computers. I can't upgrade to SP2 and I can't patch SP1 therefore I can only rely on the Antivirus which only detects the virus after infection.