This one has me stumped so I hope that someone out there can figure out what I am missing. This will be kind of long since I want to be thorough. I recently reinstalled Windows XP Pro on a Dell Dimension 330 for a small office client because it was replaced and they were passing the machine down to someone that had been using a very old computer and they wanted it to have a clean install for the new user. So I reinstalled XP and all drivers and software that they normally use with no apparent problems. Then I copied the user's profile from the old computer to the replacement as I normally do when moving people so that everything shows up the same way it did on their old computer. Again, no apparent problems. Everything runs fine, nothing missing, and no errors. That is, until the user tries to log off, restart, or shut down Windows. Then it gets a blue screen error "STOP: 0x0000004E (0x00000099....) PFN_LIST_CORRUPT". Searching on Google seems to indicate that this is either a virus or a device driver error. I knew it couldn't be a virus, but I scanned the system with Stinger, Malwarebytes, and ComboFix just to be sure and nothing was found. I installed WhoCrashed and it says that the crashes were most likely caused by NTOSKRNL.EXE. I checked the Event Viewer and it doesn't even have a reference to the crashes at all, which is pretty surprising to me because I've never seen a blue screen that didn't have at least one error entry in the Event Viewer. I verified that all device drivers are current (reinstalled all of them), ran SFC /SCANNOW to check for missing Windows files, and when that didn't work, did a full repair installation of Windows from the XP CD. The computer is still getting the same blue screen error, and still only when shutting down, rebooting, or logging off. This happens when I create a completely new user account and try to shut down or reboot with that account as well so it doesn't appear to be a problem specific to the user. I also ran MEMTEST and Prime95 (separately) for about 8 hours each and SeaTools (Seagate hard drive) as well as the built in Dell diagnostic tools and none of them found any errors. Cliff Notes: Fresh install of Windows XP runs normally while being used, except when it is logged off, rebooted, or shut down, and then it gets a PFN_LIST_CORRUPT blue screen error. Any suggestions?