Hi Vog Following your advice about the Sasser worm, I downloaded the Macafee “Stinger” removal tool. I followed all instructions (including disabling System Restore). Stinger reported finding the Sasser worm and removing it. At this point I posted my “thanks” message to you and checked the “problem solved” box. However….. ten minutes later while I was still on the internet, I got the dreaded error report again, and the computer duly shut down. I ran the Stinger again and it found nothing. Having had a look at the manual removal instructions, I have checked in the c:\windows folder and cannot see the file AVSERVE.EXE. I have also looked in the registry and cannot see the “avserve” value in HKEY_LOCALMACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run. If you have any other suggestions to solve this problem I would be enormously grateful!