MBR2GPT /validate failed [duplicate]

Solution 1:

At the moment my BIOS is not specifically set up to boot in UEIF mode (the option is there). But the Secure Boot option is enabled.

Following advice I have found I tried using MBR2GPT to see if I could convert my C drive and then change to booting in UEIF mode. But when I run the validation routine:

C:\WINDOWS\system32>mbr2gpt /validate /disk:0 /allowFullOS
MBR2GPT: Attempting to validate disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
Disk layout validation failed for disk 0

The current partition layout of your disk does not satisfy the requirements to be convert to GPT using MBR2GPT. It appears MBR2GPT is unable to proceed due to the following requirement and is the reason the disk layout validation fails.

• There is enough space not occupied by partitions to store the primary and secondary GPTs:
  • 16KB + 2 sectors at the front of the disk
  • 16KB + 1 sector at the end of the disk

The other requirements to use MBR2GPT is as follows:

• The disk is currently using MBR
• There are at most 3 primary partitions in the MBR partition table
• One of the partitions is set as active and is the system partition
• The disk does not have any extended/logical partition
• The BCD store on the system partition contains a default OS entry pointing to an OS partition
• The volume IDs can be retrieved for each volume which has a drive letter assigned
• All partitions on the disk are of MBR types recognized by Windows or has a mapping specified using the /map command-line option

A word of caution, even if you were to perform the conversion, you don't really have any enough free space on what appears to be a very small system disk to install Windows 11.

Source: MBR2GPT Disk Prerequisites