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Bob Arthur's avatar
Bob Arthur
Copper Contributor
Oct 28, 2021

Problems with partitions when using MBR2GPT

I'm not sure how to proceed to prepare for Windows 11. When running mbr2gpt, I get the following:

 

C:\WINDOWS\system32>mbr2gpt /validate /allowFullOS
MBR2GPT: Attempting to validate disk 2
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
Cannot find OS partition(s) for disk 2

 

Here's my disk layout:

I got to this point thinking I needed to delete the Recovery Partition. It now is the 861MB Unallocated partition.

What should I do to prepare for a successful run of mbr2gpt?

My system is as follows and is running Windows 10 Pro 21H1:

AMD Ryzen 5 5600x, 32GB RAM, Asus Tuf Gaming Pro X570 Wifi

 

The OS being used (C Drive) was a clone of that on the G Drive. The intent of the clone is to provide a backup and to move the OS from a smaller drive to a larger, newer one.

mbr2gpt
preparation
Windows 10
windows 11
  • SalmanAhmed's avatar
    SalmanAhmed
    Steel Contributor
    Oct 28, 2021

    Hi Bob Arthur 

    As I can see from the screenshot, following points seems pretty good for disk 2:

    • There must be a maximum of three primary partitions in the MBR partition table
    • You should not have any extended/logical partition, all three partitions must be primary partitions.
    • You must have active partition on disk 2

    The following requirement is missing on disk 2:

    • There must be a system partition (OS Partition)

    Please have a look and let me know your feedback.

    • Bob Arthur's avatar
      Bob Arthur
      Copper Contributor
      Oct 28, 2021

      Thank you for responding SalmanAhmed! I very much appreciate your willingness to help.

      So mbr2gpt is attempting to convert the original C drive (now G) and not finding an OS partition, even through Windows is installed on both the current C drive and the original C drive, which is now the G drive? I had thought it was going to change the disk with the OS currently being used (with the C and E partitions. That is why I was trying to delete the System Recovery for that drive, to get Disk 1 to three partitions.

      I was moving to the 1 TB drive to make more room for the OS, but see that it has somehow filled up. I'm not sure how that happened but I suspect it may have to do with MS Flight Simulator having been installed (although the majority of its files should be on the E drive.

      • SalmanAhmed's avatar
        SalmanAhmed
        Steel Contributor
        Oct 28, 2021

        You're most welcomeBob Arthur ,

        I've just noticed that there is no target disk specified in your mbr2gpt command, please execute as below in elevated (Run as Admin) mode in cmd:

        mbr2gpt /validate /disk:2 /AllowFullOS

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