Here is where I first saw the exploit: http://hackaday.com/2009/09/09/windows-7-and-vista-crash-via-smb-exploit/
Microsoft’s release, with helpful information on what it is and how to fix it, is here: http://www.microsoft.com/technet/security/advisory/975497.mspx
Test if your computer is affected here: http://sinisterware.blogspot.com/2009/09/smb-check.html
SMB: Server Message Block Only computers with SMB 2.0 are affected.
<writers block, forcing forward, quality not tested>
This vulnerability can lead to to remote code execution, which is not good. If you are lucky, you only get BSODed.