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How do you reset the MBR of the second physical disk?


I currently bought a new harddrive. This one was put in as Primary/slave. After having tried to install Linux, I ended up screwing up the MBR on the second disk. My question is how I can reset the MBR on the second physical disk drive. I have tried the "fdisk /mbr" command, and it successfully (and unfortunately...) wipes the mbr of the first disk. Will I have to disconnect the first drive, and then put my new one up as the first hard-drive to be able to reset the MBR?
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Do you have additional information on FDISK /MBR?

Additional Information:

FDISK /MBR is an undocumented Microsoft DOS command available in MS-DOS 5.0 and above. MBR is short for Master Boot Record. When doing FDISK /MBR it will reinstall the first 446 of 512 bytes of information with zeroes effectively rewriting the executable code and data strings that may currently be residing there. The remainder of the 512 bytes is the boot settings which tells the computer how to boot. These settings are left alone.

Q.) Does doing FDISK /MBR more then one time have any effect on the computer?
A.) As you can see in the above explanation on FDISK /MBR this command will only rewrite the executable information with zeroes. Therefore if this command is done more then once it will only be rewriting the zeroes with additional zeroes and have no additional affect.

Q.) How can I recreate the Master Boot Record on a different hard disk drive other then my primary hard disk drive?
A.) Use FDISK /CMBR <drive number> where 'drive number' represents the drive you wish to recreate the master boot record. To determine this number run fdisk and display the partition information.
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ok if you have someone running windows 98/ME with norton utilities 2002 running, then goto the command propt on that PC and then go to C:\windows\command

In this directory there will be a copy of norton Utilities for dos 2002. Copy this to a floppy (~640K) and then build a system disk, copy all system files over so the floppy is bootable. Then write an autoexec.bat file and copy that to the floppy to.

The batch file should contain the following commands:
@Echo off
Echo Starting NDD for Windows 98

When you have written the batch file and coppied it to the floppy disk use it to boot into NDD and then choose to diagnose disk. It will see that you have an MBR issue and will repair it.

If you cannot get hold of these ites i can make you one in 10 mins and post it to you, address needed for this...

Send postal address to

Since fdisk is a DOS utility, you should be able to just disable the first disk in the BIOS and fdisk should then no longer see it.  

Before doing fdisk /mbr again, just run fdisk and see if the first disk disappears.  That should do it, otherwise, yes, just unplug the first disk.

Are you sure you need to reset the MBR on the second disk?

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Many thanks to all of you for your answers. Since I now have two completely wiped disks (where the second one has a bad MBR), I think it is easiest for me to use the fdisk /cmbr 2 command. Luckily I had backed out most of my data before I started "experimenting", so all I really have to do is to install a few OS's. Hopefully the fdisk /cmbr 2 will solve the problem....

Thanks again!
I take it then that this problem is now resolved from the help of an Expert or Experts. If this is the case then the procedure here at EE is to close the question.

To close the question look for and click on the "Accept comment as answer" text that resides to the right of the Experts name right above the comment you feel best helped you resolve your problem. Now when you click on that text you should see right above the comment box a grading scale.


Select one of these and then click the "Submit" button. The question is now moved to the PAQ (Previously Asked Questions) section and for all intent and purposes is considered closed.
Avatar of Gazza08



well, I tried the "fdisk /cmbr 2" command when I came back home from work yesterday, and still fdisk is not able to "see" my second harddrive. I have also tried to boot with Partition Magic from floppy disks, but this doesn't work either. My entire second harddrive is marked as bad, and the only options I get is to "Format", "set Active" and "Information". Then, when I try to format it, I get an error message saying this is not possible because there's a "BADMBR" (error message #104).

So I am sorry to say that this matter isn't closed yet (at least not for me). Are there any other ways I can get my completely new harddrive back to the state it was in when I bought it?

Thanks again for all the efforts you have made in helping me. I will of course close the question when I have a solution, or when there seems to be no solutions left :-)

Some BIOS's have an option in it to do a lowlevel format of the drive. I would suggest taking out your other drive so you just have this problem drive left in the system so you can work with it directly and to be sure the other one isn't interfering in some manner. Also if you used PM to partition or setup this disk then fdisk is not the best way to deal with the disk. You need to use PM to fix the problem if it can then have it wipe out the disk.
Points to Crazy One;en-us;69013

No comments added lately, so it's time to clean up this TA.
Please leave any comments here within the next 4 days.
My recommendation in the Cleanup topic area will be:

PAQ - Refund
Note: CO already rcv'd 100pts (A) from Dbrunton for this above link

Please don't accept this comment as answer!
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