Follow this steps to repair your HardDisk boot record.

1. Boot from the Vista installation CD
2. Click Repair your computer
3. In System Recovery Options dialog box, click Command Prompt.
4. At the command prompt, type in Bootrec with the option you want
eg: bootrec /FixMbr
(type this will fix the master boot record)

bootrec /FixMbr

The /FixMbr option writes a Windows Vista-compatible MBR to the system partition. This option does not overwrite the existing partition table. Use this option when you must resolve MBR corruption issues, or when you have to remove non-standard code from the MBR.

bootrec /FixBoot

The /FixBoot option writes a new boot sector to the system partition by using a boot sector that is compatible with Windows Vista. Use this option if one of the following conditions is true:
The boot sector has been replaced with a non-standard Windows Vista boot sector.
The boot sector is damaged.