Problem booting Windows 2012R2 VM on Windows 2025 Hyper-V

Stefan Cuypers 100

We're having a problem with a Windows Server 2025 Hyper-V cluster.

We have 2 identical clusters (same hardware, same BIOS version) and when we move a Windows 2012R2 VM from one cluster to another it does not boot any more (tested with 2 different VM's).

The error is a blue screen 0x7B (INACCESSIBLE_BOOT_DEVICE).

If we move the machine back to the other cluster it boots just fine.

Only difference I see is the cluster path level. The working cluster is an older Windows Update (KB5058411, KB5058523 and KB5054979).

Whereas the newer cluster has KB5063666, KB5062553, KB5056579 and KB5059502. It tried installing KB5064489 also, but that does not help.

A VM with Windows server 2022 of 2025 does move fine, so it seems to be linked to 2012R2.

I also tried to install a brand new 2012R2 VM from the original iso and then completely upgrading it with Windows Update and that machine is working fine. It seems to have the same verson of storage drivers as the non working VM.

The faulting VM does boot succesfully into recovery mode. I tried bootrec /fixmbr and bootrec /fixboot, but that does not help.

TPIT 1 Reputation point

2025-07-21T03:47:13.84+00:00

Same issue here. Sadly I could not pin down the exact faulty update!

but thanks for your direction!

Thought, I killed my VM. Even the back up…. :D

Answer accepted by question author

Vladimir Shebaldenkov 140 Reputation points

2025-11-08T21:48:11.8233333+00:00

I compared the registry of a VM that boots with one that doesn’t and found some differences.

Then I booted into recovery mode, copied the missing registry keys, and successfully booted the Windows Server 2012 R2 VM on a 2025 Hyper-V host.

reg load HKLM\TempHive c:\Windows\system32\config\SYSTEM

reg copy HKLM\TempHive\ControlSet001\Enum\ACPI\VMBus HKLM\TempHive\ControlSet001\Enum\ACPI\MSFT1000 /s

reg copy HKLM\TempHive\ControlSet001\Enum\ACPI\Hyper_V_Gen_Counter_V1 HKLM\TempHive\ControlSet001\Enum\ACPI\MSFT1002 /s
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13 people found this answer helpful.
Bjørn Bendix 10 Reputation points

2025-11-09T10:54:45.4333333+00:00

Works perfect! Thx for your work!

TPIT 1 Reputation point

2025-11-09T12:25:02.85+00:00

Thanks !

Hammer 0 Reputation points

2025-11-09T20:50:35.9533333+00:00

Worker for me too! Thank you!!!

Stefan Cuypers 100 Reputation points

2025-11-10T08:12:41.2766667+00:00

Great work! Works for me too. Thanks a lot.

Andy Bryant 20 Reputation points

2025-11-10T09:51:03.03+00:00

Works for me too. Awesome job! Thank you @Vladimir Shebaldenkov

Richard Hunt 0 Reputation points

2025-11-11T06:31:51.77+00:00

Could you not just export the two keys and then import them in the same HKLM/System/CurrentControlSet/Enum/ACPI root or must be done in recovery mode and in must use ControlSet001 ?

Stefan Cuypers 100 Reputation points

2025-11-11T08:44:48.1+00:00

Some more analysis on what in KB5060842 triggers the problems.

Analysing the ACPI configuration in the BIOS it seems that the ids of some devices have changed.

The 'VMBus' name was defined as an _HID (hardware id).

After the update it is defined as a _CID (compatible id) and MSFT1000 has become the _HID.

Same applies for the Hyper_V_Gen_Counter_V1 device which has become _HID MSFT1002.

Though this should theoretically not pose a problem (Windows should look at both _HID and _CID's) it seems Windows 2012R2 (or older Hyper-V integration services on it) has a problem with this for boot devices.

Glenn Rimington 0 Reputation points

2026-02-09T23:01:29.45+00:00

FANTASTIC!!!! - That worked for me too. Thank you.

Peter Jericho 0 Reputation points

2026-02-09T23:20:11.7033333+00:00

Worked straight away. Thank you.

MARKO TAMM 0 Reputation points

2026-02-26T20:02:00.2866667+00:00

Thank You very much, You saved me alot of time :)

Mulani, Waqas 0 Reputation points

2026-03-01T08:12:38.1733333+00:00

I wanted to let you know that this fix works for me as well.

Thank you so much for all your effort in finding this solution.
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Manuel Enrique Benavides 5 Reputation points

2025-09-13T19:37:29.6633333+00:00

The only thing that worked for me was downgrading the Windows 2012 virtual machine from Gen2 (GPT - UEFI) to Gen1 (MBR - EFI) with the operating system disk in a IDE port.

For this process, I used AOMEI Partition Assistant to convert the disk from GPT to MBR, then deleted the UEFI partition. On a new Gen1 virtual machine, I performed a clean install using the same AOMEI. I copied the system partition (350MB) to the old disk mark this partition as Active, then booted with the Windows disk to repair the startup:

bootrec /fixmbr

bootrec /fixboot

bootrec /scanos

bootrec /rebuildbcd

After that, I rebooted the virtual machine, performed a disk check, and it started working correctly again on the new Windows 2025 host.
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Problem booting Windows 2012R2 VM on Windows 2025 Hyper-V

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