Whether it be due to hard disk corruption, or more likely a boot kit or rootkit, you may need to rewrite the Master Boot Record.
Rewrite the MBR in XP:
Boot into XP Disk, repair mode, recovery console
and press enter
Vista and 7 (32 or 64 bit)
To run the Bootrec.exe tool, you must start Windows RE. To do this, follow these steps:
- Put the Windows Vista or Windows 7 installation disc in the disc drive, and then start the computer.
- Press a key when you are prompted.
- Select a language, a time, a currency, a keyboard or an input method, and then clickNext.
- 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.exe, and then press ENTER.
The Bootrec.exe tool supports the following options. Use the option that is appropriate for your situation.
Note If rebuilding the BCD does not resolve the startup issue, you can export and delete the BCD, and then run this option again. By doing this, you make sure that the BCD is completely rebuilt. To do this, type the following commands at the Windows RE command prompt:
- bcdedit /export C:\BCD_Backup
- cd boot
- attrib bcd -s -h -r
- ren c:\boot\bcd bcd.old
- bootrec /RebuildBcd
The /FixMbr option writes a Windows 7 or 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.
The /FixBoot option writes a new boot sector to the system partition by using a boot sector that is compatible with Windows Vista or Windows 7. Use this option if one of the following conditions is true:
- The boot sector has been replaced with a non-standard Windows Vista or Windows 7 boot sector.
- The boot sector is damaged.
- An earlier Windows operating system has been installed after Windows Vista or Windows 7 was installed. In this scenario, the computer starts by using Windows NT Loader (NTLDR) instead of Windows Boot Manager (Bootmgr.exe).
The /ScanOs option scans all disks for installations that are compatible with Windows Vista or Windows 7. Additionally, this option displays the entries that are currently not in the BCD store. Use this option when there are Windows Vista or Windows 7 installations that the Boot Manager menu does not list.
The /RebuildBcd option scans all disks for installations that are compatible with Windows Vista or Windows 7. Additionally, this option lets you select the installations that you want to add to the BCD store. Use this option when you must completely rebuild the BCD.