If your system won’t start even in Safe Mode, all is by no means lost. You can repair many serious problems with the Windows Recovery Environment. If the trouble stems from a corrupted system file, the Windows Recovery Environment might be able to get your system running again with almost no intervention or effort on your part.
If you have a Windows Vista distribution DVD, you can get to the Windows Recovery Environment as follows:
Insert the Windows Vista DVD and restart your computer. Let the computer boot from the DVD.
You might need to change boot settings in your BIOS to enable booting from the DVD drive.
When you reach the Install Windows screen, ...