Need to fix Windows Boot Manager settings that I screwed up.

Question

I'm trying to setup a computer running Windows 10 to operate in multi-boot. The documentation I've been able to find is anything but precise. It is likely that I've screwed up and created some issues that I don't know how to correct. The BCDedit command produces the listing that follows:

*** Start List ***

Windows Boot Manager
--------------------
identifier              {bootmgr}
device                  partition=\Device\HarddiskVolume1
path                    \EFI\Microsoft\Boot\bootmgfw.efi
description             Windows Boot Manager
locale                  en-US
inherit                 {globalsettings}
default                 {current}
resumeobject            {d464cfdc-7a7f-11ee-848b-fdbf264256fa}
displayorder            {current}
                        {d464cfe0-7a7f-11ee-848b-fdbf264256fa}
toolsdisplayorder       {memdiag}
timeout                 30
displaybootmenu         Yes
Windows Boot Loader
-------------------
identifier              {current}
device                  partition=C:
path                    \Windows\system32\winload.efi
description             P1Win10
locale                  en-US
inherit                 {bootloadersettings}
recoverysequence        {d464cfde-7a7f-11ee-848b-fdbf264256fa}
displaymessageoverride  Recovery
recoveryenabled         Yes
isolatedcontext         Yes
allowedinmemorysettings 0x15000075
osdevice                partition=C:
systemroot              \Windows
resumeobject            {d464cfdc-7a7f-11ee-848b-fdbf264256fa}
nx                      OptIn
bootmenupolicy          Standard
usefirmwarepcisettings  No
Windows Boot Loader
-------------------
identifier              {d464cfe0-7a7f-11ee-848b-fdbf264256fa}
device                  partition=C:
path                    \Windows\system32\winload.efi
description             P4Win10
locale                  en-US
inherit                 {bootloadersettings}
recoverysequence        {d464cfde-7a7f-11ee-848b-fdbf264256fa}
displaymessageoverride  Recovery
recoveryenabled         Yes
isolatedcontext         Yes
allowedinmemorysettings 0x15000075
osdevice                partition=C:
systemroot              \Windows
resumeobject            {d464cfdc-7a7f-11ee-848b-fdbf264256fa}
nx                      OptIn
bootmenupolicy          Standard
usefirmwarepcisettings  No

*** End List ***

This came about as a result of my running the /copy command which produced the second Windows Boot Loader section. I then attempted to designate the partition containing my alternate version of Windows 10 as the device to be booted for the second section. However, my change which appears to have contained the wrong drive designation ending changing the section identified as {current}. This had the effect of causing a boot failure when attempting to boot that partition. Fortunately the copied section did work and I can still boot the computer. Now I notice that everything (Windows Boot Manager and both Windows Boot Loader sections) are using the same value for the identifier ( {d464cfe0-7a7f-11ee-848b-fdbf264256fa} ). I sort of think this is wrong even though I do not know anything about the purpose of those values. This leaves me stuck trying to figure what to do now. I'm tempted to create another copy since I'm pretty sure it had a unique identifier when first created and the my screw-up caused then to all become the same.

Would appreciate it if someone could provide a little guidance on what to do now.

Answer 1

Hello Snookred,

Thank you for posting in Q&A forum.

Here are some steps you can follow to fix the Windows Boot Manager on Windows 10:

1. Use another working computer to create a Windows 10 installation USB or DVD. You can download the Windows 10 installation tool from the Microsoft website.
2. Insert the installation media into your computer and restart it. You may need to change the boot order in your BIOS settings to boot from the USB or DVD. Press the appropriate key (usually F2, F12, ESC, or DEL) to enter the BIOS menu. Save your changes and restart.
3. Once the system boots from the media, choose your language preferences and click Next. Click the Repair your computer option on the bottom left of the screen. This will take you to the Windows Recovery Environment (WinRE).
4. In the WinRE menu, select Troubleshoot, then Advanced options, and finally Command Prompt. Run Bootrec Commands:

bootrec /fixmbr

bootrec /fixboot

bootrec /scanos

bootrec /rebuildbcd

These commands will fix the master boot record, write a new boot sector, scan for Windows installations, and rebuild the boot configuration data (BCD) file.

5. Type exit to close Command Prompt and restart your computer. Remove the installation media before restarting.

References：

How to Fix Windows Boot Manager Windows 10: Step-by-Step Guide

How to Repair Windows Boot Manager, BCD and Master Boot Record (MBR)

I hope the information above is helpful.

If you have any questions or concerns, please feel free to let us know.

Best Regards,

Daisy Zhou

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

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Answer 2

Thanks for the advise. I have not yet had a chance to review everything you reference. However, I did make some progress before seeing your response but now things have really gone south so to speak.

I, think, I was able to cleanup the problem I created by running BCDboot as follows:

BCDboot /bcdclean

The I was able to redo the copy as follows:

BCDedit /copy

After that I was able to use BCDedit, in what I think was a more correct manner, to customize the new entry to reference the alternate partition that I wanted to boot. I used the DISM command with the /apply-image option to add the initial content to the alternate partition. The image file (install.wim) came from the primary partition which does boot as expected. I then use Regedit, with the load hive option, to correct the MountedDevices entries so that the proper drive would be identified as C:. However, when I try to boot the alternate partition the system hangs.

I have been able to do this successfully in the past. However, it was long enough ago that I cannot say with certainty that I'm doing things the same way. Of course that also means that the newer software that I'm working with now most certainly has changed.

Finally, subsequent to using regedit to update the MountedDevices settings on the alternate partition neither one boots. They both hang. I hope to restore the image file to the same partition on which it was made to correct this problem but that will have to happen on another day.

Answer 3

Looks like another screw-up on my part. Failing to understand how Regedit works when trying to edit the registry on another partition (i.e., load hive) I apparently changed it on the system I was using and that caused it to fail on the next boot without fixing the failure to boot on the newly created partition (i.e., the one I intended to edit). Once I discovered what I'd done wrong everything is now working as expected/desired.

I would like to apologize for my failures but do appreciate the help provided and maybe this post will help someone else trying to do something similar.