There is a new Worm out there called the "Sasser" which isexploiting the MS hole defined in http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx.  MS has created a web, http://www.microsoft.com/security/incident/sasser.asp, page to help clean your PC if you are infected.

If infected with the Sasser and your PC keeps on shutting down after about 60 seconds due to the LSASS.EXE error you should print the instructions from the following web pages...
     WinXP à http://www.microsoft.com/security/incident/sasser_printxp.asp
     Win2000 à http://www.microsoft.com/security/incident/sasser_print2000.asp

You will also need to patch the hole as there is another worm call Gaobot which also exploits this hole and a few others.  If infected it blocks all attempts to open the home pages of most Antivirus companies...i.e. www.symantec.com, www.sophos.com, www.mcaffee.com, etc.  It will also attempt to kill many of the processes of many antivirus and security programs.

     Sasser à http://www.symantec.com/avcenter/venc/data/w32.sasser.worm.html
     Gaobot à http://www.symantec.com/avcenter/venc/data/w32.gaobot.afj.html