Reset or clone UEFI install using MBR partition from external drive?  

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  1. Posts : 20
    Windows 10
       #1

    Reset UEFI install using MBR partition from external drive?


    Hi folks,

    I recently made the mistake of moving my boot partition (pro tip: don't do that) and ended up re-installing Win10 from scratch. Trouble is, my drivers are all wonky now, and I'm finding it to be a hassle to manually copy over my files & re-install software.

    I have a copy of my former C:\ partition - not an image, a byte for byte copy - on an external USB drive. I also have an image of the partition, made using EaseUS Todo Backup, but something seems to be wrong with it - in comparison with the other images I've made using the same tool, this one doesn't let me look inside and see the individual files.

    What would be the best way to re-create my original install?

    Caveat: the original was set up as a BIOS/MBR partition, and with the re-install, I had to switch to UEFI/GPT (Win10 install media refused to legacy boot). So I don't think I can just clone the partition back - I have already tried this and had to re-install again :/

    Advice appreciated! Thanks in advance :)
    Last edited by jfrench; 12 Mar 2021 at 21:17.
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  2. Posts : 18,364
    Windows 11 Pro
       #2

    You clone the original OS partition back, and then use the bcdboot command to replace the BCD in the EFI system partition.
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  3. Posts : 40,988
    windows 10 professional version 1607 build 14393.969 64 bit
       #3

    Consider using Ubuntu / Linux to recover any important files.
    Set the BIOS to your preference.
    UEFI is optimal.
    Clean install Windows 10 > re install drivers and applications > restore files


    Create a bootable USB stick on Windows | Ubuntu
    Linux to the rescue! How Ubuntu can help a computer in distress | PCWorld
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  4. Posts : 20
    Windows 10
    Thread Starter
       #4

    NavyLCDR said:
    You clone the original OS partition back, and then use the bcdboot command to replace the BCD in the EFI system partition.
    I am pretty sure I tried this after my clean install (certainly tried it A LOT immediately after I borked my partition setup) and it did not work.

    Are you certain this works in my particular case (MBR original partition, EFI clean install)?

    In any case, I may try it again. Using bcdboot, where do I copy from, and where do I copy to?



    - - - Updated - - -

    zbook said:
    Consider using Ubuntu / Linux to recover any important files.
    Set the BIOS to your preference.
    UEFI is optimal.
    Clean install Windows 10 > re install drivers and applications > restore files
    Thanks...I have already done exactly as you describe (used a Ubuntu LiveUSB to retrieve files and edit partition table to GPT before re-installing Win10).

    The last part of your post - reinstall drivers and applications - is exactly what I'm trying to avoid, since I'm already having problems with the drivers.
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  5. Posts : 40,988
    windows 10 professional version 1607 build 14393.969 64 bit
       #5

    What were the driver problems?

    Partitions can be copied from MBR to GPT or GPT to MBR using 3rd party software.

    Typically a clean install corrects underlying unknown problems.
    Many end users report faster boot, improved performance, etc.


    You can try the method that NavyLCDR posted.
    The clean install can be used as the backup plan.
    Alternatively you can clean install and test any driver.
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  6. Posts : 18,364
    Windows 11 Pro
       #6

    jfrench said:
    I am pretty sure I tried this after my clean install (certainly tried it A LOT immediately after I borked my partition setup) and it did not work.

    Are you certain this works in my particular case (MBR original partition, EFI clean install)?

    In any case, I may try it again. Using bcdboot, where do I copy from, and where do I copy to?
    To use bcdboot, you must first assign a drive letter to the EFI system partition. Let's say you assign the drive letter W: to the EFI system partition, and your Windows partition has the drive letter C:. The command would be:

    Code:
    bcdboot C:\Windows /s W: /f UEFI
    You will need to change the drive letters C: and W: to match what your current drive letter assignments are, though. That can be determined by running:
    Code:
    diskpart
    list vol
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  7. Posts : 20
    Windows 10
    Thread Starter
       #7

    zbook said:
    What were the driver problems?

    Partitions can be copied from MBR to GPT or GPT to MBR using 3rd party software.

    Typically a clean install corrects underlying unknown problems.
    Many end users report faster boot, improved performance, etc.


    You can try the method that NavyLCDR posted.
    The clean install can be used as the backup plan.
    Alternatively you can clean install and test any driver.
    Thanks for the response! Could you please tell me which 3rd party software would accomplish that (GPT / MBR translation)? I am unfamiliar with Windows, having used it for about a year. The previous 20 odd years of computer use have been about half on Mac OS, and then Ubuntu until recently.

    I am glad to be upgraded to EFI boot, but the clean install has created more problems than it solved. Driver issues - the original install had Bluetooth headphones working fine, and I actually reverted to an earlier system restore point because a driver update broke things (could no longer see the switch to turn Bluetooth on / off). On my current clean install, the Bluetooth is unusable due to audio crackles / dropouts. I don't understand why there is such a range, given that the drivers I'm using are whatever is from Dell for this machine, or installed by Windows.

    - - - Updated - - -

    NavyLCDR said:
    To use bcdboot, you must first assign a drive letter to the EFI system partition. Let's say you assign the drive letter W: to the EFI system partition, and your Windows partition has the drive letter C:. The command would be:

    Code:
    bcdboot C:\Windows /s W: /f UEFI
    You will need to change the drive letters C: and W: to match what your current drive letter assignments are, though. That can be determined by running:
    Code:
    diskpart
    list vol
    Awesome, thank you!! I understand this now.
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  8. Posts : 18,364
    Windows 11 Pro
       #8

    You can use Macrium Reflect Free or MiniTool Partition Wizard to copy the partition. But you will need to use a version of the program on a bootable USB flash drive. Macrium Reflect Free has the option to create a bootable flash drive. The flash drive it creates will also have a command line interface that you can run the bcdboot command from - and it also has a utility to Fix Windows boot problems under the restore menu which would work as well.

    Remember, you only want to clone/copy the C: drive Windows partition.
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  9.   My Computer


  10. Posts : 20
    Windows 10
    Thread Starter
       #10

    NavyLCDR said:
    You can use Macrium Reflect Free or MiniTool Partition Wizard to copy the partition. But you will need to use a version of the program on a bootable USB flash drive.
    Awesome, I'm going to try this sometime this weekend I think. Thanks so much for your help!

    - - - Updated - - -

    This is great, thank you so much! Just what I was looking for. Will report back with my results.

    - - - Updated - - -

    Hi all, thanks to your help I did manage to get cloned and booted into my imaged C: partition! Woohoo!

    One odd thing: every time I restart, at first I get the message "No boot devices available. Press F1 to retry / F2 for setup / " etc. When I hit F1, the boot completes. Any ideas on how to make this go away?

    In any case, I am cautiously rejoicing at my newly recovered computer! Thank you so much for all your help! Macrium truly is amazing.
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