When your computer crashes and you see one of the following stop codes: Stop 0x000000ED (UNMOUNTABLE_BOOT_VOLUME) or Stop 0x0000007B (INACCESSIBLE_BOOT_DEVICE) the NTOSKRNL is confused. Either it cannot find the rest of itself, or it cannot read the file system at the location it believes it is stored.
When troubleshooting this error, your task is to find out why the Windows kernel is confused and fix the cause of the confusion. File system corruption might be the problem.
Insert the Windows installation disc. Launch the recovery console from the Windows installation disc and run the chkdsk /f /r command. It will detect if the File system is corrupted. If it is corrupted, run the Repair Windows option, which will replace the corrupted files with the original ones from the disk.
Note: if Windows doesn't boot, you can access the Windows installation disk by pressing F12 (F2 or F8), immediately after you restart or turn on the computer.