Analysis on MBR2GPT Conversion Failed and How-to Fix in Windows 10

August 11, 2017

Get trouble in using MBR2GPT disk conversion tool in Windows 10, cannot find OS for disk 0 or conversion failed? Don’t worry, this essay will tell you why and how.

What does MBR2GPT.EXE Windows 10 do?

MBR2GPT.EXE is first known in Windows 10 version 1703, also known as Windows 10 Creator’s Update. It is a built-in utility that located in Win\System32 directory and need to be operated in Command Prompt. According to Microsoft, MBR2GPT.EXE converts a disk from Master Boot Record (MBR) to GUID Partition Table (GPT) partition style without modifying or deleting data on the disk.

Why do we need MBR2GPT on Windows 10? In the past, when we convert partition style between MBR and GPT, we need to copy files to another place, repartition hard drive and reinstall the system, and then restore the data. It takes a lot of time and effort, and for computer newcomer, it is an error-prone process. However, MBR to GPT conversion takes only a few seconds if we work with MBR2GPT utility. No matter within the Windows PE environment or within the currently running OS, this tool allows us to convert any attached MBR-formatted system disk to the GPT partition format.

How to use MBR2GPT disk conversion tool properly?

The command of using MBR2GPT is quite simple yet there are many factors we need to pay attention to before starting conversion.

Matters needing attention

  • As covered before, the MBR2GPT tool is available only in Windows 10 version 1703 or later. To find out the Windows 10 version, we can open Settings, navigate to System > About, scroll down a bit, and the “version” word will appear.

  • If the disk has BitLocker-encrypted volume, it is suggested to suspend it first before conversion. To resume BitLocker later, we need to delete the existing protectors and recreate them.

  • Make sure the device supports UEFI and control the primary partition amount for new UEFI partition. Or, we may encounter MBR2GPT prompt: “validation failed for disk 0: Too many MBR partitions found, no room to create EFI”.

MBR2GPT tutorial

1. Type “cmd” in Windows 10 search box, find “Command Prompt”, right-click it, select “Run as administrator” and hit <Enter>.

2. (Optional) We can run “mbr2gpt /validate /disk:0” to check whether the disk is eligible for conversion. If any of these checks fails, the conversion will not proceed and an error will be returned.

3. Type “mbr2gpt /convert /allowfullos” and hit <Enter>. If want to specify a particular disk, we can type “mbr2gpt /convert /disk 0 /allowfullos”. Normally, the conversion will be done in a short while.

MBR2GPT Convert AllowFullOS

4. When the conversion has successfully completed, we need to boot to UEFI firmware settings, and switch the firmware to boot to UEFI mode instead of Legacy BIOS (CSM) (learn how to change Legacy to UEFI).

Tips:

  • If get application conflict error, it is suggested to use MBR2GPT in Windows PE environment. The command would be: “mbr2gpt /convert /disk: n”.

  • The disk is repartitioned to create an EFI system partition (ESP) if one does not already exist.

  • If dual boot Windows 10 with any other operating system, above tutorial is not suitable. This tutorial is only meant for a standalone Windows 10 installation on a PC.

  • If the existing MBR system partition is not reused for the ESP, it is no longer used by the boot process after the conversion. Other partitions are not modified.

  • If the disk is already GPT-formatted, the tool will report an error.

Why does MBR2GPT conversion failed and how to fix?

Mostly, MBR2GPT works quite well. Nevertheless, in a few cases, MBR2GPT will disappoint us. Let’s find out reasons for these failures and what we can do to remedy them.

MBR2GPT failed with return codes

According to Microsoft documents, MBR2GPT has following return codes and each code has its corresponding description. From below chart, we can easily find out what results in conversion fail and what to do to fix the error.

MBR2GPT Return Codes

Layout conversion failed

Sometimes, the MBR2GPT will give us a message instead of error code. This was discussed before actually. MBR2GPT will fail due to unsupportable Windows 10 versions. For instance, if we have MBR2GPT convert on Windows 10 version 1607, chances are that we’ll get this prompt:

LayoutConversion: Layout conversion failed. Error: 0x00000032[gle=0x00000032]; Cannot perform layout conversion. Error: 0x00000032[gle=0x00000032]

Running on Windows 10 other versions such as versions 1507 and 1511 may also get this outcome. As a result, to fix this error, we can run the tool while booted into Windows 10 version 1703 or later, and perform an offline conversion.

“MBR2GPT cannot find OS” when converting data disk

Some users report that MBR2GPT cannot find OS partition for disk 0 when doing the conversion. As mentioned before, MBR2GPT is used to convert any MBR-formatted SYSTEM disk to GPT. That is to say, it will not work for data disk that has no OS installed. To convert such data disk from MBR to GPT, it is suggested to backup all data, delete all partitions and do the conversion in Disk Management. If the Windows 10 OS does have been installed on the disk that is about to convert and we still get the error, it is time to seek help from other MBR to GPT conversion tool.

Workaround for MBR2GPT not working – AOMEI Partition Assistant

AOMEI Partition Assistant Professional is reliable and powerful hard drive partition manager that can also help us convert system disk from MBR to GPT without data loss in Windows 10 all versions. This convert software will solve aforementioned MBR2GPT conversion failed issue perfectly. Other issues like “MBR2GPT not found”, “MBR2GPT missing” and “MBR2GPT can only be used from the Windows Pre-Installation Environment” will be fixed at the same time. It has graphical user-friendly interface that is suitable for every computer user.

What’s more, it allows us to convert GPT to MBR in Windows 10 on the contrary if the need ever arises in the future. Windows 7, 8/8.1, XP and Vista are supported by this software as well.

Simple steps to convert MBR to GPT via MBR2GPT utility equivalent

1. Download, install and launch this MBR2GPT alternative. In the main interface, right click the disk and select “Convert to GPT Disk”.

Convert Win10 System to GPT

2. Click “OK” in the pop-up dialog to confirm the operation. It will prompt us the GPT is boot from UEFI mode.

Confirm MBR to GPT Conversion

3. View the virtual result. The disk has changed to GPT disk from MBR and all partitions and data are kept. Click “Apply” > “Proceed” to commit the pending operations.

Apply

Tips:

  • Switch the firmware to boot to UEFI mode after conversion.

  • To convert MBR to GPT in Windows PE with AOMEI Partition Assistant, we can use "Make Bootable Media" feature to achieve the task. 

  • To convert MBR to GPT in Server 2012 or Server 2016, please refer to AOMEI Partition Assistant Server edition.

Except for converting between partition styles, AOMEI Partition Assistant also can assist us convert among file systems without formatting. Download this tool to discover more.