I use Windows XP (Im not sure of the version or anything like that, as I currently cannot get into my system) on a computer home-built by my dad.

Yesterday morning I came down to find my computer, which had been on all night, constantly restarting, trying to load windows and failing. It doesnt give any sort of message, it just gets to a certain point and starts over.

When I try to boot in safe mode, it shows the list of all the files as they load, and the one that it displays immediately before restarting is "mup.sys". I tried replacing it with the mup.sys from an older hard drive, but it did not work. A memory diagnostic shows no problems with the drive itself, and Im not sure what to do next.

Resources I have at my disposal include Hirens Boot CD, the Ultimate Boot Disc (an old version), and a Gentoo Linux boot CD.