How can I change mbr to gpt without data loss?

Indeed, MBR2GPT.exe is a popular command line tool provided by Microsoft in Windows 10 and Windows 11. It converts a disk from MBR (Master Boot Record) to GPT (GUID Partition Table) without losing data. This tool is mainly used to prepare systems for UEFI boot mode, which is required for features like Secure Boot and Windows 11 installation.

It's typically used when upgrading from BIOS to UEFI, especially for modern hardware or during in-place OS upgrades.

However, there are the most common issues and problems when you use it to convert or change mbr to gpt in Windows, along with brief explanations and possible solutions.

Issue 1. "Disk layout validation failed for disk 0"

Cause: The disk does not meet the layout requirements in order to change mbr to gpt without data loss.

Fix:

Ensure the disk uses MBR and has a maximum of 3 primary partitions.

Delete any unnecessary recovery or OEM partitions if needed.

Use diskpart to check partition structure:

diskpart
list disk
select disk 0
list partition

Issue 2. "MBR2GPT cannot find OS partition(s)"

Cause: The tool can't find a valid Windows installation.

Fix:

Make sure the system partition is marked as active and contains boot files.

Boot from Windows PE or recovery media if running inside Windows fails.

Try using the tool with the /allowFullOS flag if you’re running it from a live OS.

3. BitLocker Errors

Cause: BitLocker encryption can prevent the conversion.

Fix:

Suspend BitLocker before running the tool:

manage-bde -protectors -disable C: