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Duel Installations of Windows/Duel Boot Drives

Kyle Styles 0 Reputation points
2025-08-12T04:36:24.3866667+00:00

I have a custom-built gaming PC that I have upgraded over the years. I more recently upgraded to running my OS and drives on an NVMe M.2 Samsung EVO 960 250GB SSD. Then I upgraded and tried to install my OS on an NVMe M.2 Gen 4 Inland 2TB SSD. I vaguely recall an error message appearing, suggesting that I may have been running two instances of Windows, one on my Samsung and one on my Inland. Somewhere in the process, I managed to get through the errors, booted to my OS, and everything was working fine. I left it. However, I'm now running into an issue where I cannot convert my SSDs from MBR to GPT all so I can see if I can enable secure boot, update to TPM 2.0, and update to Windows 11. Also, so I can play Battlefield 6. Throughout trying countless options, I discovered that Windows thinks I have two boot drives now.

This is where I tried to complete a fresh install of windows using the media creation tool. I booted to a formatted USB Flash Drive and ran the setup. The setup would not complete because it stated there was already an instance of Windows installed.

I have reached my wits' end and am tired of Googling solutions. Can someone help me get my system cleaned up, updated, and running Battlefield 6, please? Oh, and also, now that I’ve been messing around with stuff, my system won’t find my Samsung drive anymore, despite it being listed as “healthy” and connected in disk management. It won’t appear in the file explorer as an accessible drive.

Here's what I've tried so far, not an exhaustive list:

Command Prompt

-MBR2GPT /CONVERT /(either primary disk) /ALLOWFULLOS

-Fails stating: “Disk layout validation failed for (whatever disk)

-MBR2GPT /VALIDATE /(either primary disk) /ALLOWFULLOS

-Same result

Reading the error logs (Windows-setupact.log) when trying to convert the Inland disk, it says:

-MBR2GPT: Validating layout, disk sector size is: 512 bytes

-ValidateLayout: Wrong boot partition count, expected 1 but found 0.

Reading the error logs (Windows-setupact.log) when trying to convert the Samsung disk, it says: -Cannot find OS partition(s) for disk 0

Tried “clean all” on both disks, did not work as it thinks both drives are primary boot. Tried 3rd party software called NIUBI Partition to convert and it gives the error: -“This disk contains system/boot volume, you are not allowed to convert because it will cause system unbootable."

Can someone help me find the solution? I’ve backed up what I need, so I’m not afraid of a system wipe but would like to try to avoid that.

Thank you in advance for your help.

Windows for home | Windows 10 | Windows update
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  1. Volume Z 150 Reputation points Volunteer Moderator
    2025-08-12T04:54:15.18+00:00

    Hello,

    first off please provide an image of Disk Management.

  2. Hendrix-V 230 Reputation points Microsoft External Staff Moderator
    2025-08-12T09:07:51.91+00:00

    Hello Kyle Styles,

    Thank you for reaching out to the Microsoft Q&A Forum!

    I understand you’re experiencing issues with dual Windows installations on separate NVMe drives, preventing you from converting to GPT and enabling Secure Boot for Windows 11. If validation fails, you’ll need to clean up the boot configuration first.

    Here are some steps and considerations to resolve this:

    1 - Confirm Current Boot Configuration

    • Open Disk Management and verify which disk holds the active EFI System Partition (ESP).
    • If both drives have boot partitions, Windows may be confused about the default boot loader.

    2 - Backup Your Data

    Since you’ve already backed up critical files, proceed with caution. If not, please back up before making changes.

    3 - Clean Up Boot Entries

    Open Command Prompt (Admin) and run:

    bcdedit /enum all

    Identify duplicate or invalid entries and remove them using:

    bcdedit /delete {identifier}

    4 - Convert to GPT

    Once only the correct boot partition remains:

    mbr2gpt /convert /disk:<disknumber> /allowFullOS

    5 - Enable UEFI and Secure Boot

    • After conversion, switch your BIOS from Legacy/CSM to UEFI mode.
    • Enable Secure Boot and TPM 2.0 for Windows 11 compatibility.

    6 - If issues persist, the most reliable method is:

    • Disconnect the secondary drive.
    • Perform a clean install of Windows on the primary drive in UEFI mode.
    • Reconnect the secondary drive and format it for storage or reinstall Windows if dual boot is still desired.

    To assist others who might have similar questions and to help us improve our support system, we kindly encourage you to "Accept the answer" if it successfully addressed your concern. Accepting an answer lets other users know that this solution worked for you, and it also helps us track the effectiveness of our support efforts. 

    Warm regards, 

    Hendrix Vu | Microsoft Q&A Support Specialist

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