Support for Windows Vista without any service packs installed ended on April 13, 2010. To continue receiving security updates for Windows, make sure you're running Windows Vista with Service Pack 2 (SP2). For more information, refer to this Microsoft web page: Support is ending for some versions of Windows
A Windows Vista-based or Windows 7-based computer does not start because the master boot record (MBR) has been corrupted. When you try to use the Startup Repair tool to fix the MBR, the Startup Repair tool reports that no problem was found.
Note You can access the Startup Repair tool on the Windows Vista or Windows 7 installation disc that is appropriate for your version of Windows.
When a USB flash drive is inserted in a computer, the computer hardware sometimes reports that the USB flash drive is the system partition. The Startup Repair tool examines the USB flash drive instead of the actual system partition on the hard disk. Because Startup Repair cannot locate the corrupted MBR, it does not detect a problem.
To avoid this behavior, remove the USB flash drive before you run the Startup Repair tool.
For more information about how to troubleshoot startup issues in Windows Vista, click the following article number to view the article in the Microsoft Knowledge Base:
927392 How to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows Vista