Manually Rebuilding a Windows Boot Partition (MBR)

Neemobeer

Windows Forum Team
Staff member
In this tutorial we will be manually creating the system boot partition. This is for a system that is BIOS booting (sometimes referred to as legacy or legacy CSM) which utilizes the MBR.

The MBR is the first sector on the hard drive that contains a small first stage boot loader which hands the boot process to a larger more sophisticated boot manager. This boot manager resides on the System Reserved partition seen in the image below.

Here we have a pretty standard disk. If you have a couple extra partitions that's ok. The process is fairly similar.
37327


Now I've removed the system partition.
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You will need to create a bootable USB or DVD installer of your OS, although technically you could use a Vista or Newer OS disc as the tools are pretty much the same.
Now we will boot to the install media and click next after selecting your language.

  • Click on "Repair your computer"
  • Click on Troubleshoot
  • Click on Command Prompt
If you're starting with no system partition
The first thing we need to do is to create our system partition
At the command prompt type the following.
  • Type diskpart
  • Type list disk
  • If you only have 1 disk then type select disk 0
  • If you have multiple disks, you will want to select each in turn and type detail disk to identify the correct disk. Most of the time you will have the system partition on the same drive as the C volume. Typing detail disk will show you what volumes are on the selected disk

  • Now create the partition with create part primary
  • Type list part and ID the newly created partition. (If the system partition was deleted the new partition will be the same size and less than 1GB)
  • Now select the partition with select part # where # will be the number identified from the list command
  • With the new partition selected mark it active by typing active
  • Now format the partition with format fs=ntfs quick label="System Reserved"
  • Type list vol and make note of your new partition
  • Type select vol # where the # is the number assigned to your volume
  • Type assign letter E the letter can be any non-assigned drive letter (we'll need this in a later step, also make note of your OS assigned letter [it might not be C])
  • We're all done preparing the disk so type exit
If the system partition exists and you just cant boot start here
Now it's time to prepare or repair the system partition
  • First we need to make sure the system partition has a valid MBR on it by typing bootrec /fixmbr
  • Now we need to copy critical system files and BCD store. From my example above my system partition is E and my OS is C type the following bcdboot C:\Windows /s e:
Now type exit to close the command prompt and click on Continue to boot
 

donR

New Member
I'd just like to say this forum has been very helpful over the years so thanks for all the contributers and usually I can solve my windows problems here.

I'm wondering if rebuilding the MBR will fix this new problem I am having? See below.

I have installed windows on my new SSD Disk 0 but unfortuantely it still requires my old Disk 1 to boot up which I want to replace with a larger drive. I'm thinking the MBR is still on Disk 1 rather than Disk 0 and I believe it is something to do with the "RECOVERY" partition being on Disk 1 instead of Disk 0.

If I go through the steps above for Disk 0 will it solve my problem so that I can remove Disk 1?

Thanks

Disk Partitions 2.jpg
 
Last edited:

Mike

Windows Forum Admin
Staff member
Premium Supporter
To confirm your suspicions,

Open an elevated command prompt (Search -> cmd.exe -> Right-click "Run as Administrator")
Enter: bcdedit /enum

If you want to post the output here it should tell us what is going on.
 

Neemobeer

Windows Forum Team
Staff member
The boot partition is nothing more than what gets Windows to load. You can add a boot partition to the other disk or a new disk. The easiest method though would be, if you're going to use a new disk is unplug the other disks and the Windows installer will create a new boot partition. You may also want to consider changing your firmware to boot UEFI and use GPT partition disks.
 

donR

New Member
To confirm your suspicions,

Open an elevated command prompt (Search -> cmd.exe -> Right-click "Run as Administrator")
Enter: bcdedit /enum

If you want to post the output here it should tell us what is going on.
Thanks, I should have mentioned I did try to rebuild the boot record and went through the steps with bootrec but ultimately bootrec /fixboot came up with "element not found"

This is the print out from enum but doesn't mean much to me:

bcdedit enum.jpg
 

donR

New Member
The boot partition is nothing more than what gets Windows to load. You can add a boot partition to the other disk or a new disk. The easiest method though would be, if you're going to use a new disk is unplug the other disks and the Windows installer will create a new boot partition. You may also want to consider changing your firmware to boot UEFI and use GPT partition disks.
Thanks, I thought the above and I did unplug my old Disk 1 and used a windows recovery USB, but windows could not fix itself and as mentioned above the bootrec repair/steps on the new Disk 0 did not work either with ultimately it saying "element not found" which led me to believe the MBR must be on Disk 1

My only other thought is to try an "upgrade" and hope windows reinstalls itself without deleting all my software/programs which is why I'm hesitant to let it do a re-install.

I'm not familar with the UEFI and partition disks but did find this procedure if you think it would work?

 

donR

New Member
Thanks for everyone's replies so far.

Just wondering if anyone else had any more thoughts? Still unsure which is the best way forward. thanks Don
 

xsta

New Member
Thanks for everyone's replies so far.

Just wondering if anyone else had any more thoughts? Still unsure which is the best way forward. thanks Don
Don try BCDboot.exe..I tried bootrec/fixMBR, bootrec/RebuildBCD, bootrec/fixBoot, no dice. Then bcdboot worked, but ONLY if U assert the Proper partition/drive name. For some unbeknown reason, bloody WinInstaller/winRepair disks jumble up the naming of yr partitions, so refer to yr "enumeration" and check the name of System Partition. If it's C:, (where normally WD be d: in a running OS on Disk Mgt) then use:
bcdboot C:\Windows \s D:/l en-us Replace the d: with whatever yr OS is on (the one W sys32 on it). This should copy yr OS version of BCD data to your faulty System Partition(\mbr store of BCD). The MBR is in System Parttn. It has BCD, as does yr OS. If it doesn't work, Google "how to type correct commands for bcdboot.exe" as I'm certain this copy is how U should fix yr BCD in system pttn/MBR. I was on it for days.....it worked but I'm now just trying to learn why other .exe's couldn't copy it also.
 
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