If you are having trouble getting Windows Vista to startup due to a corrupted Master Boot Record, you can use the Windows Recovery Tools to restore it. To do this, perform the following steps:
1. Start your computer using the Windows Vista installation disc.
2. Choose Repair your computer from the main screen.
3. Choose the operating system you wish to repair and click Next.
4. Click Command Prompt on the next screen.
5. At the command prompt, type bootrec.exe /fixmbr.
6. A message should appear stating The operation completed
Try to start your computer again and pray it will fix the issue.