Registry crash in XP Pro?

I don't know what the bejeezus is up, but one night everything is running fine and the next morning I can't get into XP Pro <i>at all</i>.

I get as far as the loading screen and then a quick blank screen followed by a blue screen that lasts for < 1 sec before rebooting. From what I can make out from the many times I've tried to read it, it says there is a registry error "error c0000128" it can't load a "...(hive) file" from a directory "<windows root>\system32\prog\xxxxx" (<---- I don't have the specifics in front of me on the path, but I can get it if necessary). The safe mode screen comes up prior to loading, but none of the options makes any difference.

The main reason I'm confounded is that I didn't add a program or otherwise change any registry setting between the time it was running fine and the endless looping cycle of blue screen -> reboot that started the next morning.

I'm curious if this is some virus or possibly a hard disk failure where the missing file is located. Any helpful info would be nice. If there is a FAQ or link on this kind of problem, point the way. It's on a RAID 0 array (with no backup) so if it means an XP reinstallation, I can deal. If it means a HD format...that will suck more than slightly. :\