By Emily / Last Updated September 22, 2021

The error: MBR2GPT validation failed

MBR2GPT is a tool designed by Microsoft to help people convert a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. It’s very useful when you own a hard drive larger than 2TB and want to make full use of it. It’s also needed when you plan to create more than 4 primary partitions. Now, Microsoft officially declared that Windows 11 system only allows UEFI, the command of conversion from MBR to GPT increases greatly.

Despite the convenience MBR2GPT utility brings us, some people are disappointed by MBR2GPT errors. Here is a user sharing the experience of encountering MBR2GPT validation failed problem:

“I am using a 4TB HDD as a storage drive on my pc, with a 500GB SSD for the OS and other programs. I am only able to partition 2TB of my HHD due to it having an MBR partition style, and would like to convert it to GPT so I can use all of its available space. The 2TB partition is almost full and only has 67GB remaining, which is why I am trying to convert it.

After using the command 'mbr2gpt /validate /disk:1 /allowFullOS', I get the message 'Disk layout validation failed for disk 1'. How can I fix this?”

To solve the problem, we may figure out the causes first.

Causes and solutions to MBR2GPT validation failed

Here I'm going to show you two possible causes for MBR2GPT validation failure and corresponding solutions:

Inapplicable Windows system

MBR2GPT program only applies to Windows 10 version 1703 (also known as the Creator's Update) or later. An inapplicable Windows system can lead to an MBR2GPT disk layout failure.

▪ if you are using a computer running Windows 7, 8, or 8.1, please upgrade the operating system to Windows 10.

▪ if you have installed earlier versions of Windows 10 such as versions 1507, 1511, and 1607, you must run the tool while booting into Windows 10 version 1703 or later and perform an offline conversion.

Non-system disk

MBR2GPT is a tool to convert any attached MBR-formatted system disk to the GPT partition format. You cannot use it to convert non-system disks from MBR to GPT. If you do want to convert a data disk, you can convert MBR to GPT in Windows 10 via Disk Management or Command Prompt. However, you are at risk of losing data because you have to delete all partitions or volumes on the disk before conversion.

Fix MBR2GPT validation failed via MBR2GPT alternative

If you meet MBR2GPT conversion failure, you can turn to an MBR2GPT alternative-AOMEI Partition Assistant Professional that can help you convert MBR to GPT without data loss quickly and safely.

What’s more, it overcomes MBR2GPT’s shortcomings. For example, it applies to all Windows 10 versions as well as Windows 7, 8/8.1, XP, and Vista. And it can not only convert a system disk from MBR to GPT but also a storage disk. Next, I’ll show you how to fix MBR2GPT validation failed quickly via AOMEI Partition Assistant in detail:

PS.: you can download the demo version to have a free trial.

Download Free Demo Win 11/10/8.1/8/7/XP
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Step 1. Install and launch AOMEI Partition Assistant. Right-click the disk you want to convert and select “Convert to GPT Disk”.

Convert MBR Disk to GPT

Step 2. Click “OK” in the pop-up dialog to confirm the operation. If you are converting a system disk, you will get a prompt that the GPT disk boots from UEFI mode.


Step 3. Click “Apply” to commit the operations.


▪ For converting a system disk, you must switch the firmware to boot from UEFI mode after conversion.
▪ To convert MBR to GPT in Windows PE with AOMEI Partition Assistant, please use the “Make Bootable Media” feature to complete the task.
▪ AOMEI Partition Assistant can also convert GPT to MBR without data loss in reverse.


To fix the MBR2GPT validation failed error, please ensure you are running Windows 10 1703 or later versions. Or if you don't mind data loss, you can use Disk Management or Command Prompt for MBR to GPT conversion. The best solution is to use AOMEI Partition Assistant, so you don't need to care about OS version or data loss. 

You can also format an external hard drive in RAW and stop checking the file system on C in Windows 7 via AOMEI Partition Assistant. Get this tool and enjoy all the wonderful functions now!