To convert disk from MBR to GPT:
1. Start Windows 10 Installation by booting from USB/DVD
2. On the very first screen open terminal (SHIFT+F10)
3. In order to convert disk, it's number must be identified. To do so type in following commands:
- list disk - identify disk number to convert. You can determine correct disk number by size of disk. Note that number.
4. Now the conversion:
- mbr2gpt /convert /disk:X (replace X with identified disk number)
5. Successful conversion will have following output:
MBR2GPT will now attempt to convert disk 0.
If conversion is successful the disk can only be booted in GPT mode.
These changes cannot be undone!
MBR2GPT: Attempting to convert disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
MBR2GPT: Trying to shrink the system partition
MBR2GPT: Trying to shrink the OS partition
MBR2GPT: Creating the EFI system partition
MBR2GPT: Installing the new boot files
MBR2GPT: Performing the layout conversion
MBR2GPT: Migrating default boot entry
MBR2GPT: Adding recovery boot entry
MBR2GPT: Fixing drive letter mapping
MBR2GPT: Conversion completed successfully
MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!
6. Restart computer, don't forget to change boot mode to UEFI.
based on: https://docs.microsoft.com/en-us/windows/deployment/mbr-to-gpt
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