INACCESSIBLE_BOOT_DEVICE

One morning when I powered up my computer, I received the lovely
INACCESSIBLE_BOOT_DEVICE message on my computer, which runs Windows
2000 Professional SP4. I had not done any hardware or software
upgrades. I have tried all kinds of tools, and I have always been
able to see my drives (I have two SCSI drives), so I am pretty sure it
isn't a hardware problem. I finally broke down and installed another
copy of the same OS (not any service packs though), on the same drive
but in a different folder, and I can boot successfully from that
installation now. I am however still getting the
INACCESSIBLE_BOOT_DEVICE when I try to boot to the original
installation. In the BOOT.INI file, the only difference in that the
old installation is showing WINNT and the new TEMPWIN. The
INACCESSIBLE_BOOT_DEVICE message shows up about half way through the
colorfull Windows screen if that helps anything. I have tried to boot
in both Safe Mode and Last Known Good Configuration with the same
outcome. Does anyone know what I can try next? Are there files I can
copy from the new installation to the old, or are there other steps I
can try. My guess is that one of the files has became corrupt, but I
have no idea which one. I did try booting with loging turned on, but
if I've done my research correctly, the ntbtlog.txt file isn't created
until later.

Thanks for any advice,

Tor