A Full Guide to MBR2GPT.EXE Tool

If you have started a Windows 11 upgrade in your corporate environment, you may have heard about MBR2GPT. MBR2GPT.exe is a tool that helps convert the disk partition style on Windows PC from the legacy Master Boot Record (MBR) to GUID Partition Table (GPT) without changing or deleting data on the hard drive.

This article will teach you about the MBR2GPT tool for Windows 10 and 11 and how you can use it yourself.

Part 1. What Is MBR2GPT Tool on Windows 10/11?

MBR2GPT.EXE converts a disc from the Master Boot Record (MBR) partition style to the GUID Partition Table (GPT) partition style. It is designed to be run from a WinPE (Windows Preinstallation Environment) Command Prompt. However, with the /allowFullOS option, the program can also be launched from the entire Windows 10 operating system (OS).

The MBR2GPT tool can be found in the directory Windows\System32 on PCs running Windows 10 version 1703 or later and Windows 11.

Both Windows PE and the complete OS environment have this utility available. You must first upgrade the Windows PE image (winpe.wim, boot.wim) with the Windows ADK 1703, or a later version, in order to utilize this tool in a deployment task sequence using Configuration Manager or Microsoft Deployment Toolkit (MDT).

Part 2. How To Use the MBR2GPT Tool?

1. Converting Within Full Windows OS Environment

Open the command prompt by typing cmd in the search box of the Windows 10 toolbar. In the cmd elevated command prompt, type mbr2gpt /convert /disk: n /allowfullOS. The disk partition you wish to convert appears. Press Enter, and you are done.

2. Converting Within Windows PE

The process is the same. However, here you have to type in different commands.

Part 3. The Limitations of MBR2GPT

Though MBR2GPT looks like a day-savior tool, it does come with some limitations.

Part 4. Troubleshooting When Using MBR2GPT

The tool can return various common errors. But don't worry, as you can resolve them in most cases. Here is the list of return codes you may get when using the MBR2GPT utility:

Fix #1: MBR2GPT Disk Layout Validation Failed

This is one of the most common errors we find during the MBR to GPT conversion. It may be due to the wrong syntax or system you are using. MBR2GPT.exe only applies to Windows 10 version 1703 or later. The error can also occur if your system does not support the BIOS you are converting.

To solve this, check the following:

You can also refer to this video for a complete guide to fix the "MBR2GPT disk layout validation failed" error.

Fix #2: MBR2GPT Cannot Find OS Partition

There could be many technical reasons behind this error. The most common one is that your system has bad entries in the boot configuration. Check the video below to solve this problem quickly.

Here is also a step-by-step guide for you to fix “MBR2GPT can’t find OS partition”:

Step 1. Open the diskpart and check for any bad entries. Use the syntax as follows:

▸diskpart
▸select disk 0: the operating system disk
▸list partition
▸select partition 2: because here partition 2 is the partition where the Windows OS is installed
▸assign drive letter= w (for example)
▸select partition 1: because here partition 1 is the system-reserved partition
▸assign drive letter= b (for example)

After this, you can easily take a step ahead of the system boot partition files to examine the Windows system partition further and determine whether the boot folder is present.

Step 2. Use the command "X: Sources>dir /a w: " Run the command "X: Sources>dir /a b: " to verify the system-reserved partition if the necessary boot folders are not present.

Step 3. After locating the boot folder in the system partition or system reserved partition, you must use the command "X: Sources>dir /a b: Boot" to launch the bcdedit program and direct it to the location of the boot configuration data store you just located.

Step 4. Identify any invalid entries at this point. Type "X: Sources>bcdedit /store B:bootbcd /enum all" to run the command. There are numerous cues for incorrect or subpar entries. For instance, "unknown" might be found in a few entries. They might be left over from an earlier Windows installation or brought on by malicious software.

Step 5. Copy the bad entry's identification. Next, navigate to the store once more with bcdedit and instruct it to remove the error-prone entry using the copied identifier. Finally, take The Bad Entry Out.

Step 6. To see if everything is working correctly now, try running the command "X: Sources>bcdedit /store B:bootbcd /enum all" once more. If everything goes as planned, use the MBR2GPT utility once more. This time, you can finish it successfully.

Check out this video to learn more about the process in a visual format.

Fix #3: MBR2GPT Is Not Recognized

The leading cause of this version is your Windows version. You will get this error if you run any version other than windows 10 or 11.

To fix this error, you may simply upgrade your windows to version 10, and this error will not occur again. You can check your Windows version using the System Information dialogue box.

Fix #4: MBR2GPT Cannot Find Room for the EFI System Partition

This error comes up when you don't have enough free space on your computer's system or C allocated drive. In some cases, this error can also occur if there is no unallocated disk space on your system.

You can remove this error by shrinking the C drive to form a new unallocated space. Then, you can move the unallocated space to the front partition of the disk. You can also use any third-party tool to perform this step. Make sure to back up data before proceeding.

Summing up

We hope this article was an eye-opener for you. Remember that facing errors during MBR2GPT tool conversion is a typical process. You will get a chance to learn the intricacies of the computer system while using this tool. Good luck.