1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when the message indicating "press any key to boot from cd or dvd" appears.
3. Select a language, a time, a currency, and a keyboard or another input method.
4. Click repair your computer.
5. Click the operating system that you want to repair, and then click next.
6. In the systems recovery options dialog box, click command prompt.
7. Type bootrec /rebuildbcd , and then press enter.