I have XP SP3 and while I was using it today, it just shut off randomly and attempted to reboot. I had made no changes to any system files, or installed anything, etc...
When it attempted to reboot, it froze at the logo screen, and wouldn't progress no matter how much time was left for it. I attempted to boot in safe mode, and the usual list of system files and drivers ran down the screen, stopping at Mup.sys it froze there repeatedly. I've attempted to boot the Windows Recovery Console, to no avail. I have been unable to locate my xp cd to attempt to repair from it.