MBR2GPT.EXR doesn't work

Question

Hello,my disk where windows is currently running is MBR and I wanted it to go to GPT but when I used MBR2GPT gave me an error which said failed for disk:0.Ive tried shrinking the disk but still fot the same error.Is there anyone that knows how to fix this error so I can switch to GPT?

Answer 1

MBR2GPT only supports a maximum of three primary partitions on the disk. So, if there is more than that, delete a partition.

If you find a hidden System Reserved Partition, you can try removing it using a third-party partition manager.If there's no unallocated space, right-click on your main partition (C drive) in Disk Management and select "Shrink Volume." Allocate enough space (a few hundred MB should suffice) to create unallocated space.

1. Open an elevated command prompt and choose "Run as administrator".
2. Type the following command, replacing <driveletter> with your actual boot disk drive letter (usually C):

      mbr2gpt /convert /allowfullos /disk:<driveletter>
   

   • /allowfullos flag allows conversion with the OS installed on the disk.

Answer 2

Hi Makis Akritidis,

Thanks for your reply. Based on my research, regard the command of /allowFullOS. By default, MBR2GPT.exe can only run from Windows PE and is blocked from running in full Windows. This option overrides this block and enables disk conversion while running in the full Windows environment. Also please note: Since the existing MBR system partition is in use while running the full Windows environment, it can't be reused. In this case, a new EFI system partition is created by shrinking the OS partition.

Reference: MBR2GPT - Windows Deployment | Microsoft Learn

Best Regards,

Ian Xue

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