Problem with master boot record

[Phil Jollans]

Hi,

I am trying to repair an installation of Windows XP Home on a PC which
formerly had a dual boot configuration with Linux.

Rebooting the system during the repair failed and I figured that this was
related to the dual boot configuration.

I have tried to fix it from the recovery console, using the FIXMBR command,
but so far without success. I have run the repair installation a couple of
times, but it always fails to reboot.

The FIXMBR command always shows the error message

This computer appears to have a non-standard or invalid master boot record.
FIXMBR may damage your partition tables if you proceed. This could cause all
the partitions on the current hard disk to become inaccessible. If you are
not having problems accessing your drive, do not continue. Are you sure you
want to write a new MBR?

(Actually it shows it in German, but it is the equivalent message.)

I enter Y and it claims to have written the MBR, but if I enter the FIXMBR
command again, I always get the same message. This gives the impression,
that FIXMBR has not in fact worked correctly.

Can anybody explain this behaviour?

Can anybody recommend an alternative tool to update the MBR, running from a
bootable floppy or CD?

Are there any circumstances in which the windows repair installation would
write the MBR, for example if I was able to wipe is completely?

Thanks in advance
Phil

 

[Pegasus \(MVP\)]

Hi,

I am trying to repair an installation of Windows XP Home on a PC which
formerly had a dual boot configuration with Linux.

Rebooting the system during the repair failed and I figured that this was
related to the dual boot configuration.

I have tried to fix it from the recovery console, using the FIXMBR command,
but so far without success. I have run the repair installation a couple of
times, but it always fails to reboot.

The FIXMBR command always shows the error message

This computer appears to have a non-standard or invalid master boot record.
FIXMBR may damage your partition tables if you proceed. This could cause all
the partitions on the current hard disk to become inaccessible. If you are
not having problems accessing your drive, do not continue. Are you sure you
want to write a new MBR?

(Actually it shows it in German, but it is the equivalent message.)

I enter Y and it claims to have written the MBR, but if I enter the FIXMBR
command again, I always get the same message. This gives the impression,
that FIXMBR has not in fact worked correctly.

Can anybody explain this behaviour?

Can anybody recommend an alternative tool to update the MBR, running from a
bootable floppy or CD?

Are there any circumstances in which the windows repair installation would
write the MBR, for example if I was able to wipe is completely?

Thanks in advance
Phil

You can restore the MBR by booting the machine with
a Win98 boot disk from www.bootdisk.com, then running
this command: fdisk /mbr. This works equally well on FAT
and on NTFS volumes.

In view of the response you saw to fixmbr, I would back
up all important files before running fdisk.exe.

 

[Phil Jollans]

Hi,

thanks for the tip. Actually, I had already tried that.

I have now found the problem, which was that the boot sector on the
partition was corrupted. Using boot floppys with Partition Magic, I
discovered that the number of heads was set to 240 instead of 255. After
patching this, I was able to boot and continue the repair installation.

I believe that the problem is caused by an error in the Linux Bootloader
GRUB, but this might be incorrect.

Phil

 

[Timothy Daniels]

thanks for the tip. Actually, I had already tried that.

I have now found the problem, which was that the
boot sector on the partition was corrupted. Using
boot floppys with Partition Magic, I discovered that
the number of heads was set to 240 instead of 255.
After patching this, I was able to boot and continue
the repair installation.

I believe that the problem is caused by an error in
the Linux Bootloader GRUB, but this might be
incorrect.

Congratulations. How did you know that the device
(a hard drive?) had 255 heads?

*TimDaniels*

 

[Phil Jollans]

Hi Tim,

I used a utility that I found on the Partition Magic floppys which I think
was called partinfo or ptinfo. I piped the output to a file which I then
examined on another computer.

This log file showed the number of heads was 255 for the disk. It also
showed the number in the boot sector on the partition was 240.

In addition, there is a second hard drive in the computer, with ubuntu
linux, where the corresponding entries (also 255) matched.

There was another tool, I think ptedit, with which I could edit the boot
sector.

I got lucky!

I have appended the complete log file.

Phil










Partition Information Program
Aug 09 2001 - DOS32 Version
Copyright (c) 1994-2001, PowerQuest Corporation
Permission is granted for this utility to be freely copied so long
as it is not modified in any way. All other rights are reserved.

PowerQuest, makers of PartitionMagic(r), Drive Image(tm) and DriveCopy(tm),
can be reached at
Voice: 801-226-6834 Web site: http://support.powerquest.com
Fax: 801-226-8941 Email: (e-mail address removed)
BiosExtensions: 0x2100 Subsets (0x00000005): Access EDD
EGeo 0x0000 16383 16 63 156250000 0 512


============================================================================

Disk 0: 9726 Cylinders, 255 Heads, 63 Sectors/Track.

BiosExtensions: 0x2100 Subsets (0x00000005): Access EDD
The BIOS supports INT 13h extensions for this drive.

============================ Partition Tables ==============================

Partition -----Begin---- ------End----- Start Num

Sector # Boot Cyl Head Sect FS Cyl Head Sect Sect Sects

---------- - ---- ---- ---- ---- -- ---- ---- ---- ---------- ----------

0 3 80 0 1 1 07 [1023 254 63] 63 156232062
[Large Drive Placeholders]

0 1 1 9724 254 63
Actual Values

BiosExtensions: 0x2100 Subsets (0x00000005): Access EDD
EGeo 0x0000 16383 16 63 33683328 0 512


============================================================================

Disk 1: 2096 Cylinders, 255 Heads, 63 Sectors/Track.

BiosExtensions: 0x2100 Subsets (0x00000005): Access EDD
The BIOS supports INT 13h extensions for this drive.

============================ Partition Tables ==============================

Partition -----Begin---- ------End----- Start Num

Sector # Boot Cyl Head Sect FS Cyl Head Sect Sect Sects

---------- - ---- ---- ---- ---- -- ---- ---- ---- ---------- ----------

0 0 80 [ 0 1 1] 0C [1023 254 63] 63 16819992
[Large Drive Placeholders]

0 1 1 1046 254 63
Actual Values

0 1 00 [1023 0 1] 05 [1023 254 63] 16820055 16852185
[Large Drive Placeholders]

1047 0 1 2095 254 63
Actual Values

16820055 0 00 [1023 254 63] 83 [1023 254 63] 16820118 14747607
[Large Drive Placeholders]

1047 1 1 1964 254 63
Actual Values

16820055 1 00 [1023 0 1] 05 [1023 254 63] 31567725 2104515
[Large Drive Placeholders]

1965 0 1 2095 254 63
Actual Values

31567725 0 00 [1023 254 63] 82 [1023 254 63] 31567788 2104452
[Large Drive Placeholders]

1965 1 1 2095 254 63
Actual Values




==================================================================================

Disk 0: 76293.1 Megabytes

============================= Partition Information
==============================

Volume Partition Partition Start
Total

Letter:Label Type Status Size MB Sector # Sector
Sectors

------------- --------------- -------- -------- ---------- - ---------- ----------

NTFS Pri,Boot 76285.2 0 3 63
156232062

Unallocated Pri 7.8 None - 156232125
16065





==================================================================================

Disk 1: 16441.5 Megabytes

============================= Partition Information
==============================

Volume Partition Partition Start
Total

Letter:Label Type Status Size MB Sector # Sector
Sectors

------------- --------------- -------- -------- ---------- - ---------- ----------

EMILYS_C FAT32X Pri,Boot 8212.9 0 0 63
16819992

Extended Pri 8228.6 0 1 16820055
16852185

EPBR Log 7201.0 None - 16820055
14747670

Linux Ext2 Log 7200.10 16820055 0 16820118
14747607

EPBR Log 1027.6 16820055 1 31567725
2104515

SWAPSPACE2 Linux Swap Log 1027.6 31567725 0 31567788
2104452






========================================================================

Boot Sector for drive *: Drive 1, Starting Sector: 63, Type: NTFS

========================================================================

1. Jump: EB 52 90

2. OEM Name: NTFS

3. Bytes Per Sector: 512

4. Sectors Per Cluster: 8

5. Reserved Sectors: 0

6. Number of FAT's: 0

7. Root Dir Entries: 0

8. Total Sectors: 0 (0x0)

9. Media Descriptor: 0xF8

10. Sectors Per FAT: 0

11. Sectors Per Track: 63 (0x3F)

12. Number of Heads: 240 (0xF0)

13. Hidden Sectors: 63 (0x3F)

14. Big Total Sectors: 0 (0x0)

15. Unused: 0x80 00 80 00

16. Total NTFS Sectors: 156219776 (0x94FB980)

17. MFT Start Cluster: 786432 (0xC0000)

18. MFT Mirror Start Clust: 9763736 (0x94FB98)

19. Clusters per FRS: 246

20. Clusters per Index Blk: 1

21. Serial Number: 0xC8F4570AF456FA60

22. Checksum: 0x00000000

23. Boot Signature: 0xAA55





========================================================================

Boot Sector for drive *: Drive 2, Starting Sector: 63, Type: FAT32

========================================================================

1. Jump: EB 58 90

2. OEM Name: MSWIN4.1

3. Bytes Per Sector: 512

4. Sectors Per Cluster: 16

5. Reserved Sectors: 32

6. Number of FAT's: 2

7. Reserved: 0x0000

8. Reserved: 0x0000

9. Media Descriptor: 0xF8

10. Sectors Per FAT: 0

11. Sectors Per Track: 63 (0x3F)

12. Number of Heads: 255 (0xFF)

13. Hidden Sectors: 63 (0x3F)

14. Big Total Sectors: 16819992 (0x100A718)

15. Big Sectors Per FAT: 8209

16. Extended Flags: 0x0000

17. FS Version: 0

18. First Cluster of Root: 2 (0x2)

19. FS Info Sector: 1

20. Backup Boot Sector: 6

21. Reserved: 0x00 00 00 00 00 00 00 00 00 00 00 00

22. Drive ID: 0x80

23. Reserved for NT: 0x00

24. Extended Boot Sig: 0x29

25. Serial Number: 0x1B7514D8

26. Volume Name: EMILYS_C

27. File System Type: FAT32

28. Boot Signature: 0xAA55

 

[Timothy Daniels]

I used a utility that I found on the Partition Magic floppys
which I think was called partinfo or ptinfo. I piped the
output to a file which I then examined on another computer.

This log file showed the number of heads was 255 for the
disk. It also showed the number in the boot sector on the
partition was 240.

In addition, there is a second hard drive in the computer,
with ubuntu linux, where the corresponding entries (also 255)
matched.

There was another tool, I think ptedit, with which I could edit
the boot sector.

You're admirably resourceful! And I had no idea that a
PC's hard drive had so may read/write heads. And I'm
happy to know that I, also, have a copy of Partition Magic.

*TimDaniels*

 

[Phil Jollans]

You're admirably resourceful! And I had no idea that a

PC's hard drive had so may read/write heads. And I'm
happy to know that I, also, have a copy of Partition Magic.

I don't think that they actually have that number of physical heads. I think
that this parameter has become abstracted from its original meaning.

Phil