Replacing the Boot Sector
If Ntldr is damaged or missing, or if the boot sector is corrupted, you can resolve either problem by using the Recovery Console.
To start the computer and use the Recovery Console to replace the boot sector
Insert the Windows XP Professional Setup CD-ROM into the CD-ROM drive.
Restart the computer. If prompted to press a key to start the computer from the CD-ROM, press the appropriate key.
When the text-based part of Setup begins, follow the prompts. Press the R key to repair a Windows XP Professional installation.
If you are repairing a system that has more than one operating system installed, from the Recovery Console choose the Windows XP Professional installation that you need to repair.
If you press ENTER without typing a number, the Recovery Console quits and restarts the computer.
The Recovery Console might also show valid installations of Windows NT 4.0. However, the results of attempting to access a Windows NT 4.0 installation can be unpredictable.
When prompted, type the Administrator password. If you do not have the correct password, or if the security database for the installation of Windows XP Professional that you are attempting to access is corrupted, Recovery Console does not allow access to the local disks and you cannot replace the boot sector.
To replace the boot sector, at the Recovery Console command prompt, type:
If you do not specify a drive letter, the Recovery Console replaces the boot sector of the system volume. If you need to replace the boot sector of a volume that is not the system volume, then you must specify the appropriate drive letter.
Using a Disk Editor to Replace the Boot Sector
If the boot sector is not from the boot volume on the hard disk, you can use several methods to replace it. If you backed up the boot sector by using DiskProbe, then restoring it by using DiskProbe is the fastest method.
If you want to replace the boot sector on an NTFS volume, you have another alternative. When you create or reformat an existing volume as an NTFS volume, NTFS writes a duplicate of the boot sector in the following location:
At the end of the volume on volumes formatted with Windows XP Professional, Windows 2000, and Windows NT 4.0.
At the logical center of the volume on disks formatted with Windows NT 3.51 and earlier.
You can use DiskProbe to locate and copy a duplicate boot sector to the beginning of the volume. There are also third-party MS-DOS-based disk tools that you can use to locate and copy this backup boot sector to the primary boot sector on the volume.
For specifically replacing corrupted boot sectors from boot volumes, DiskProbe is not always an option. Unless you created a Windows XP Professional startup floppy disk, you cannot start Windows XP Professional, which is required by DiskProbe. You can use a third-party MS-DOS-based, low-level disk editor to restore the backup boot sector.