How to Recover From a Corrupt NTFS Boot Sector

ID: Q121517

The information in this article applies to:
  • Microsoft Windows NT operating system version 3.1
  • Microsoft Windows NT Advanced Server version 3.1
  • Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
  • Microsoft Windows NT Server versions 3.5, 3.51, 4.0
This article is part of the Windows NT Workstation Frequently Asked Questions (FAQ) available on www.microsoft.com/support/ DO NOT DELETE THIS ARTICLE. Contact your KBL if you have questions. WWWFAQ

SUMMARY

When a Windows NT system with a Windows NT File System (NTFS) partition has a corrupt boot sector, you may never get the Windows NT boot menu selections, or the following error message may appear at the boot loader screen:

Windows NT could not start because the following file is missing or corrupt <%SYSTEMROOT%>\SYSTEM32\NTOSKRNL.EXE

If you start the emergency repair process, the following message appears before the emergency repair disk restores any data:

Setup has determined that your file system is corrupt

Booting with an MS-DOS system disk and using the command fdisk /MBR does not resolve the problem. The purpose of this article is to describe a method of recovering from a corrupt NTFS boot sector. Before proceeding with this method, make sure that you have the hard disk information backed up.

Additionally, if any NTFS partition is showing as UNKNOWN in Disk Administrator and the volume is NOT part of any FT Fault Tolerant sets, this, too, can be caused by a corrupted NTFS boot sector. Following the procedure described below should allow you to run a CHKDSK against the volume and recover the data.

MORE INFORMATION

The Windows NT version 3.xx file system keeps a duplicate copy of the NTFS boot sector at the logical center of the volume, whereas Windows NT version 4.0 keeps a duplicate copy at the end of the partition. The Norton Utilities DiskEdit program can help find the duplicate boot sector and restore it over the original boot sector. You may be able to recover one NTFS partition for each hard disk or multiple NTFS and FAT-combination partitions for each hard disk.

If the partitions on the disk were created with Windows NT 4.0 and you can successfully boot into Windows NT V4.0 but have UNKNOWN partitions, please see the following Microsoft Knowledge Base article:
ARTICLE-ID: Q153973
TITLE : Recovering NTFS Boot Sector on NTFS Partitions

This article assumes you have knowledge of Primary and Extended partitions.

The following procedure describes the process of recovering one NTFS partition on a 1-gigabyte (GB) hard disk:

Run Norton Utilities Diskedit.exe from an MS-DOS boot disk, and then select Configuration on the TOOLS menu. Clear the read only check box, and then click OK button.



  1. From the Object menu, select Drive. Select the Physical disk option and select the Hard disk in question. Click OK. Norton Utilities DiskEdit should read the hard disk you selected and display Data from Cyl 0, Side 0, Sector 1.


  2. Select As Partition Table from the View menu and note the starting and ending cylinder, sector, and side information for the corrupt partition. If the corrupt NTFS partition is contained on a logical drive in an Extended partition, you will need to walk the partition table to get to the logical drive in question.


  3. Select Physical sector from the Object menu. Input the starting cylinder, side, and sector, and select the maximum amount of sectors. After you click OK, you will be at the beginning of the corrupt partition.


  4. The Primary NTFS boot sector will be found one side up. For example, if you are looking at Cyl 0, Side 0, Sector 1, go to Cyl 0, Side 1, Sector


  5. You should see something similar to the following on a good NTFS partition: 

    
00000000: EB 5B 00 4E 54 46 53 20 - 20 20 20 00 02 01 00 00
.[.NTFS.........

00000010: 00 00 00 00 00 F8 00 00 - 3E 00 0E 00 3E 00 00 00
........>...>...

00000020: 00 00 00 00 80 00 80 00 - D6 57 0A 00 00 00 00 00
.........W......

00000030: 1D 10 00 00 00 00 00 00 - EC 2B 05 00 00 00 00 00
.........+......

00000040: 02 00 00 00 04 00 00 00 - FD 1E 6F 0C 65 6F 0C 76
..........o.eo.v

00000050: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 FA 33 C0
..............3.

00000060: 8E D0 BC 00 7C FB B8 C0 - 07 8E D8 C7 06 54 00 00
....|........T..

00000070: 00 C7 06 56 00 00 00 C7 - 06 5B 00 10 00 B8 00 0D
...V.....[......

00000080: 8E C0 2B DB E8 07 00 68 - 00 0D 68 56 02 CB 50 53
..+....h..hV..PS

00000090: 51 52 06 66 A1 54 00 66 - 03 06 1C 00 66 33 D2 66
QR.f.T.f....f3.f

000000A0: 0F B7 0E 18 00 66 F7 F1 - FE C2 88 16 5A 00 66 8B
.....f......Z.f.

000000B0: D0 66 C1 EA 10 F7 36 1A - 00 88 16 25 00 A3 58 00
.f....6....%..X.

000000C0: A1 18 00 2A 06 5A 00 40 - 3B 06 5B 00 76 03 A1 5B
...*.Z.@;.[.v..[

000000D0: 00 50 B4 02 8B 16 58 00 - B1 06 D2 E6 0A 36 5A 00
.P....X......6Z.

000000E0: 8B CA 86 E9 8A 36 25 00 - B2 80 CD 13 58 72 25 01
.....6%.....Xr%.

000000F0: 06 54 00 83 16 56 00 00 - 29 06 5B 00 76 0B C1 E0
.T...V..).[.v...

00000100: 05 8C C2 03 D0 8E C2 EB - 8A 07 5A 59 5B 58 C3 BE
..........ZY[X..

00000110: 54 01 EB 03 BE 34 01 E8 - 09 00 BE A8 01 E8 03 00
T....4..........

00000120: FB EB FE AC 3C 00 74 09 - B4 0E BB 07 00 CD 10 EB
....<.t.........

00000130: F2 C3 1D 00 41 20 64 69 - 73 6B 20 72 65 61 64 20
....A disk read

00000140: 65 72 72 6F 72 20 6F 63 - 63 75 72 72 65 64 2E 0D
error occurred..

00000150: 0A 00 29 00 41 20 6B 65 - 72 6E 65 6C 20 66 69 6C
..).A kernel fil

00000160: 65 20 69 73 20 6D 69 73 - 73 69 6E 67 20 66 72 6F
e is missing fro

00000170: 6D 20 74 68 65 20 64 69 - 73 6B 2E 0D 0A 00 25 00
m the disk....%.

00000180: 41 20 6B 65 72 6E 65 6C - 20 66 69 6C 65 20 69 73
A kernel file is

00000190: 20 74 6F 6F 20 64 69 73 - 63 6F 6E 74 69 67 75 6F
too discontiguo

000001A0: 75 73 2E 0D 0A 00 33 00 - 49 6E 73 65 72 74 20 61
us....3.Insert a

000001B0: 20 73 79 73 74 65 6D 20 - 64 69 73 6B 65 74 74 65
system diskette

000001C0: 20 61 6E 64 20 72 65 73 - 74 61 72 74 0D 0A 74 68
and restart..th

000001D0: 65 20 73 79 73 74 65 6D - 2E 0D 0A 00 00 00 00 00
e system.......

000001E0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
................

000001F0: 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 55 AA
..............U.


    This is a valid NTFS boot sector. The offset (the first column on the left) is 00000000. When you have found the original NTFS boot sector, note the location (Cyl ___, Side___, Sect___). Then, you must look for the backup NTFS boot sector.

    NOTE: Below are two separate sections on locating the backup copy of the NTFS boot sector. Follow Section 1 if the partition was created under Windows NT version 3.xx or Section 2 if the partition was created under Windows NT version 4.0.

    Section 1: To Locate the Backup Copy for a Partition Created by Windows NT

    Version 3.xx



  6. Divide the total number of cylinders for the partition by two. In the example above, the total number of cylinders is 1014. Therefore, the target would be cylinder 507. It is recommended that you subtract five cylinders from that number because NTFS puts it at the logical center.


  7. Select Physical sector in the Object menu and input your cylinder number (502 for this example), side 0, sector 1, maximum number of sectors. When you click OK, you will be at that location.


  8. Select Find from the Tools menu and input the hex string 4E 54 46 53 20 and start a search for that string. When you find one, note the Cyl, Side, and Sector numbers. Make sure it is at the beginning of that sector. If it is not, continue the search until you find the string that is at the beginning. After you find the string at the beginning of the sector (and it looks similar to the original boot sector), you are ready to copy the sector.

    NOTE: It may be necessary to select As Hex from the View menu after selecting the search string if the data displayed does not appear to be in the same format.


  9. Select Physical sector in the Object menu and input the Cyl, Side, and Sector information for the backup boot sector. This time, select ONLY ONE sector (this is very important). When you click OK, you will be back at the backup boot sector. If you page down, you should only see that sector. If you are able to see more sectors after that, stop and reselect the Physical sector as one sector.


Go to Step 9 below and continue to the end.

Section 2: To Locate the Backup Copy for a Partition Created by Windows NT

Version 4.0

5. Using the partition table information found is step 2 above, note the ending cylinder, sector, and side information for the corrupt partition.

6. Select Physical sector from the Object menu. Input the ending cylinder, side, and sector, and select only one sector to read (this is very important). When you click OK, you will be at the backup NTFS boot sector. If you page down, you should only see that sector. If you are able to see more sectors after that, stop and reselect the Physical sector as one sector.

Go to Step 9 and continue to the end.

9. Select Mark from the Edit menu and use the arrow keys to select the whole sector.

10. Select Write To from the Tools menu and input the location of the original boot sector (as noted in Step 4 above). When you click OK, it will ask if you are sure. Click OK again and it will write the backup sector to the original boot sector.

11. Quit the Norton Utilities DiskEdit program, and then restart the computer.


If your original boot sector was indeed corrupt, your computer should start now, or if it was showing as UNKNOWN in disk administrator, you should be able to run chkdsk /F against the partition to make it accessible once again.

Additional query words: 3.10 3.50 3.51 4.00 virus forms bootsector

Keywords : kbnetwork ntboot ntfilesys NTSrvWkst
Version : winnt:3.5,3.51,4.0
Platform : winnt
Issue type : kbhowto


Last Reviewed: July 15, 1999
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