[How To] Convert A Disk From MBR To GPT In Windows 10 Without Losing Data

While installing Windows 10, you need to convert the Master Boot Record (MBR) disk into GUID Partition Table (GPT), if you’re installing Windows on UEFI system and MBR partition table comes in your pathway. Under such condition, you receive “Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.” message.

So this message can be suppressed with MBR to GPT conversion as described here:

Steps to convert a disk into MBR to GPT format

However, with above mentioned conversion, the biggest disadvantage is that you lose your data. Hence to deal with this problem, Microsoft has introduced a command-line utility tool, named MBR2GPT.exe available in Windows 10 Version 1703 (Creators Update) or later. This tool basically converts your MBR disk into GPT without erasing your data on the disk. In this article, we’ll discuss how to use this tool efficiently.

How To Convert A Disk From MBR To GPT In Windows 10 Without Losing Data

MBR2GPT tool can be simply executed in Command Prompt window, just like other tools such as DISM, SFC etc. The best thing about this tool is that you can also run it from Advanced Recovery Command Prompt aka Windows Preinstallation Environment (Windows PE). Error/warnings with usage of this tool are logged under %windir%.

The general syntax to use this tool is as follows:

MBR2GPT.exe /validate|convert [/disk:<diskNumber>] [/logs:<logDirectory>] [/map:<source>=<destination>] [/allowFullOS]

You can substitute following variables in above syntax, as per your requirement:

Variable	Usage
/validate	Instructs MBR2GPT.exe to perform only the disk validation steps and report whether the disk is eligible for conversion.
/convert	Instructs MBR2GPT.exe to perform the disk validation and to proceed with the conversion if all validation tests pass.
/disk:<diskNumber>	Specifies the disk number of the disk to be converted to GPT. If not specified, the system disk is used. The mechanism used is the same as that used by the diskpart.exe tool SELECT DISK SYSTEM command.
/logs:<logDirectory>	Specifies the directory where MBR2GPT.exe logs should be written. If not specified, %windir% is used. If specified, the directory must already exist, it will not be automatically created or overwritten.
/map:<source>=<destination>	Specifies additional partition type mappings between MBR and GPT. The MBR partition number is specified in decimal notation, not hexidecimal. The GPT GUID can contain brackets, for example: /map:42={af9b60a0-1431-4f62-bc68-3311714a69ad}. Multiple /map options can be specified if multiple mappings are required.
/allowFullOS	By default, MBR2GPT.exe is blocked unless it is run from Windows PE. This option overrides this block and enables disk conversion while running in the full Windows environment.

For extensive details about this tool, interested readers may head over to this Microsoft documentation.

Hope you find the tool useful!