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PC Hacks
By Jim Aspinwall
October 2004
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Fix the Master Boot Record on FAT Partitions
Use FDISK to restore the ability to boot from your FAT-16 or FAT-32 hard drive
[Discuss (0) | Link to this hack]

FDISK is a DOS program that can actually help you out of some of those nasty "unable to locate operating system" and "no boot drive available" error conditions Windows 9x and DOS users encounter from time to time. The Master Boot Record can be corrupted by an improper shutdown, power glitch, or disk failure. Re-creating a new Master Boot Record at the first sector of the hard drive—which is what your system BIOS is looking for in order to turn over the startup operation to an operating system—is an easy fix.


If your hard drive is managed by a drive overlay utility from OnTrack or a specific program provided by your drive manufacturer (as indicated by a Disk Manager or similar announcement message during bootup) or is set to boot with the GRUB or LILO boot managers, or into Linux, using this hack will destroy access to the drive.

To use FDISK's Master Boot Record restoration feature to get your main or additional drives back into bootable shape, follow these steps:

  1. Boot with a DOS diskette, boot CD, or bootable USB FLASH drive or hard drive containing DOS and FDISK. A Windows 98 or Me startup diskette will do nicely.

  2. At the command prompt type in either:



  3. Remove the disk or device you booted to DOS with and then restart the system to verify that you can boot from the hard drive.

FDISK /MBR re-creates the Master Boot Record, the first sector of the hard disk. This can be helpful to repair a damaged or corrupted bootable drive.

FDISK /CMBRx re-creates the boot sector of the first (x = 1), second (x = 2), third (x = 3), or fourth (x = 4) hard disk(s).

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