I spent the majority of yesterday and more than a few hours today trying to sort out my son's computer. Like the majority of windows users he had auto-update switched on, partly to make sure that the latest patches were installed, partly because windows nags you endlessly if you don't. During the install of the latest batch a restart was required to complete the process and fuck me if it refused to reboot.
Once it got to the "safe mode" options screen choosing any of them caused the machine to instantly restart. Venturing into the recovery console for a chkdsk /r (which took over 2 1/2 hours to go through the disk) proved the disk was still working. Try again, this time with auto-restart switched off which gave me a BSOD with an 0x00007E error code.
Research into cures for this drew blank after blank so a system restore, over 300 windows updates, re-installing the most important of his software and a new virus checker later he now has a functioning machine again. I told TLB about this and he fired me over an email brief moments ago with links to this article.
So, if you have installed a Windows XP update MS10-015 (KB977165) and it's fucked up your machine you aren't alone. If you click through the link above to the article there is a workaround which, if I'd known about it earlier, would have saved me over 5 hours of grief.
Of course if the bloody operating system didn't need patching so frequently that it demands you keep auto-update on then maybe my son would have missed the patch and the ensuing grief. I'm just glad that this machine has not, and will not, ever have a microsoft OS installed on it while under my stewardship.