My computer is not able to boot,

go straight to the second option it seems:

Get your Vista installation DVD and pop it into your drive.
- Then restart your computer.
- Press a key when you are prompted.
- Select a language, a time, a currency, and a keyboard or another input method, and then click Next
- Click Repair your computer
- Click the operating system that you want to repair, and then click Next
- In the System Recovery Options dialog box, click Command Prompt
- Type bootrec /rebuildbcd and then press ENTER

• If Bootrec runs successfully, it will present you with the installation path of a Windows directory. To add the entry to the BCD store, type Yes . A confirmation message appears that indicates the entry was added successfully.

• If Bootrec cannot locate any missing Windows installations, you must remove the BCD store, and then you must re-create it. To do this, type the following commands in the order shown below: (Remember to press ENTER after each command)

bcdedit /export C:\BCD_Backup

ren c:\boot\bcd bcd.old

bootrec /rebuildbcd

- Restart the computer.