If you are getting this warning with time limited grey box of 1 minute then shuts down then I suggest you run anti virus software.the WSBlaster worm causes this probelem but you have to get a fix here is the url for fix.
http://securityresponse.symantec.com/avcenter/venc/data/w32.blaster.worm.removal.tool.html
Also to see if it is there goto start run then type in msconfig click on setup button and if you see WS.blast.exe then it is there uncheck the box.Then goto start my computer right click that then properties than turn off system restore.Why because it is sitting in system restore and cannot be removed but if you goto fix above and then they will direct you to a patch your system will be ok. Good luck.