Over the course of 9 hours in the past two days, I have managed to eliminate the most bizarre computer problem I've ever encountered. To explain this problem, I'm going to have to lay out my general physical computer layout. My typical, working computer has two harddrives: 1 - Holds Windows, unimportant programs 2 - Holds data, most programs Last night I hooked up an old harddrive (call that harddrive 3) from a friend in place of my data HDD, so the layout was: 1 - Holds Windows 3 - Old drive with Windows This started up, but HDD 3 was assigned C:\ and HDD 1 was assigned D:\. Because of this, I couldn't format HDD 3. Anyway, I went back to the old setup of HDD1 and HDD2. Here's the problem: The computer gets stuck at the blue Windows XP screen right before the logon screen. Disconnecting all except the HDD1 doesn't change things. Here are the real problems: -Safe mode fails also -BIOS settings to Failsafe Defaults does nothing -Restoring last working settings does nothing Where it gets crazy is that reconnecting the HDD3 with Windows, but still booting from HDD1 works. The registry runs from HDD1, as do all services. Windows is indeed running from the HDD1 which will not boot, but requires HDD3. I tried another drive (HDD4) with Windows XP Home (as opposed to Windows XP Media Center on the other two) and tried to boot from that and it failed. However, booting HDD1 WITH HDD4 works. Going into Control Panel -> Administrative Tools -> Computer Management and opening Disc Management, HDD1 is listed as Healthy (System), HDD4 as Healthy (Paging). I can't change HDD4 because it's paging, so I disable that under Control Panel -> System -> Advanced Tab -> Performance -> Advanced -> Virtual Memory (Change) and change the drive letter assignment to E: and restart. System gets stuck on the blue screen. I hook up HDD3 in place of HDD4, along with HDD1 and swap the drive letter to E: and try to assign HDD1 to C:. Doesn't work because it is the System drive. Into the Registry we go: -HKEY_LOCAL_MACHINE --SYSTEM ---MountedDevices Rename the entry for \DosDevices\D: to \DosDevices\C: Restart under original set-up . . . Solved. I have a feeling I'm one of only 12 people who would have fixed that. Gotta say: You suck Microsoft. Gah.