How to Fix MBR2GPT Error in MBR to GPT Conversion in Windows 10?

July 26, 2019

While using MBR2GPT.exe to convert MBR system disk to GPT disk, the MBR2GPT error message may annoy you a lot. Here you can know some errors you may meet and how to solve it.

About MBR2GPT

MBR2GPT is a MBR to GPT conversion tool applies to Windows 10 version 1703 or later. It can convert a disk from MBR to GPT partition style without modifying or deleting data on the disk. You can run it from a Windows PE (Windows Preinstallation Environment) command prompt, or run it from the full Windows 10 operating system. MBR2GPT works with the syntax as following:

MBR2GPT /validate|convert[/disk:] [/logs:] [/map:=] [/allowFullOS]

  • /validate: to perform only the disk validation steps and report whether the disk is eligible for conversion.

  • /convert: if all validation tests pass, it will perform the disk validation and proceed with conversion.

  • /disk:: instructs MBR2GPT.exe to specify the disk number of the disk to be converted to GPT. If not specified, the system disk is used.

  • /logs:: specifies the directory where MBR2GPT.exe logs should be written. If it is specified, the directory must already exist; if not, %windir% is used.

  • /map:=: it will specify additional partition type mapping between MBR and GPT.

  • /allowFullOS: unless MBR2GPT.exe running from Windows PE, it is blocked in default. This syntax can override the block and enable disk conversion while running in the full Windows environment.

How to convert MBR to GPT with MBR2GPT conversion tool?

After learning about MBR2GPT and its syntax, here you should learn how to convert MBR to GPT with MBR2GPT.exe. Before doing that, here are the things you should know:

  • 1. The MBR disk is working with legacy BIOS mode, while the GPT disk is working with UEFI. After the disk has been converted to GPT partition style, the firmware must be reconfigured to boot in UEFI mode. Thus, you need to make sure if your device supports UEFI before converting the disk to GPT.

  • 2. You need to make sure that the current partition layout is displayed prior to conversion - a system reserved partition, a windows partition, and a recovery partition.

  • 3. For Windows to remain bootable after the MBR to GPT conversion, an EFI system partition (ESP) must be in place. If the existing MBR system partition is not reused for the ESP, it is no longer used by the boot process after the conversion.

Then, you can type the syntax in the command prompt to convert MBR to GPT disk with MBR2GPT tool.

Run the command prompt as Administrator. Type C:\Windows\system32>mbr2gpt /convert /disk:0 /allowfullos

You can see the result like the following screen shot:

MBR2GPT Convert

*The MBR2GPT tool can convert operating disk that have earlier versions of Windows 10 installed, such as version 1570, 1511, and 1607. However, you must run the tool while booted into Windows 10 version 1703 or later, and perform an offline conversion.

However, not everyone can use it successfully. You may receive many errors during the progress.

MBR2GPT error and how to fix it

MBR2GPT may return codes like following picture:

MBR2GPT Error Code

You may receive errors during the MBR to GPT conversion. And we collect some common errors and solutions for those errors here.

●“There is no room for EFI partition”

Maybe you are confusing that there is enough unallocated space, and it still shows this funny error. Actually, if you got the message: “Too many MBR partitions found” in addition to “...no room to create EFI system partition”, then the problem is that preparation is done in MBR mode and MBR limits the number of partitions to 4. for this problem, you need to check how many partitions you have with Diskpart.

●“Please remove the write protection”

If you have create a write protection for your disk, you cannot operate on it unless it deleting the protectors. So here you need to remove the write protection from the MBR disk.

“ValidateLayout: Wrong boot partition count, expected 1 but found 0”

The MBR2GPT only supports to convert MBR system disk to GPT. The data disks aren’t supported. A data disk can be backed up, converted, then restored using dism and the disk management console.

● MBR2GPT cannot find OS partition

As it mentioned before, the MBR2GPT.exe is only used to convert MBR system disk to GPT. Is there is only a data disk without OS installed, it cannot convert successfully with the error : MBR2GPT cannot find OS. For convert data MBR disk to GPT, here we suggest you copy hard drive to another place, delete all partitions on the MBR disk, then, convert MBR disk to GPT with Diskpart or Windows Disk Management.

Besides those common MBR2GPT errors, there are many others like ValidateLayout: Cannot map MBR partition type 222. Please supply custom mapping through the command line, MBR2GPT cannot perform layout conversion error 0x00000000, etc. MBR2GPT conversion failed with so many reasons. It seems a little bit annoyed. Well, is there any way to avoid MBR2GPT errors so that you can convert from MBR to GPT easier?

Convert MBR to GPT with AOMEI Partition Assistant

MBR2GPT errors will disappoint you. Fortunately, here we will introduce you a great alternative to MBR2GPT.exe - AOMEI Partition Assistant Professional, which is a great partition manager that can help you convert MBR system disk to GPT without losing data. Also, you can use it to convert data disk between MBR and GPT disk safely. Here are the detailed steps of how to convert MBR system disk to GPT with AOMEI Partition Assistant. What’s more, it works well on all Windows PC including Windows 10/8/7/Vista/XP.

*You still need to make sure if your computer’s motherboard supports EFI/UEFI mode. If not, the disk cannot boot after conversion.

Step1. Install AOMEI Partition Assistant Pro, launch it. Right click the MBR disk installed Windows OS. Select Convert to GPT Disk.

Convert System Disk to GPT

Step2. It will pop out a window to ask you if you are sure to convert MBR to GPT. Click OK.

OK to GPT System Disk

Then, it will pop out a notice to remind you to make sure if your motherboard supports EFI/UEFI mode. Click Yes.

Step3. Here you can see that the MBR disk is already changed into GPT disk. Click Apply at the tool bar to submit the operation.

Apply to GPT System Disk

  • The progress may run under the PreOS mode.

  • After MBR to GPT conversion, you should change the boot order to UEFI so that the computer can boot successfully.

Conclusion

MBR2GPT tool is a good tool for Windows 10 version 1703, and Windows creator’s update. It may work well but still existing MBR2GPT errors. While AOMEI Partition Assistant should be a great tool for all Windows PC users. You can not only convert MBR system disk to GPT, but also support convert MBR data disk to GPT without losing data. Besides, it is also a hard drive manager that you can use to repartition hard drive, convert partition between FAT32 and NTFS safely, etc. If you need to convert MBR to GPT on Windows Server, the AOMEI Partition Assistant Server supports Windows Server 2003, 2008 (R), 2012 (R), 2016.