I have a domain controller that crashed and I don't have a current backup for it. I also only have 1 domain controller. The good news is the hard drives are fine and I can access all the files. I have tried using the OS disk in other hardware and I get a BSOD saying it can't find the boot device. It sounds like a driver issue. Is there a way to change the drivers it is using to boot?
Do a repair install of Windows on the existing disk.
-Edit : They did make it more complex than it used to be. As some first steps, select command prompt, CD into recovery, and run StartRep. If you get stuck at that point, do some more reading on this stuff.
And in the future, make sure you have backups of everything important, like your domain :-)