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. The tool runs from a Windows Preinstallation Environment (Windows PE) command prompt, but can also be run from the full Windows 10 operating system (OS) by using the /allowFullOS option.
Syntax
MBR2GPT /validate|convert [/disk:diskNumber] [/logs:logDirectory]
[/map:source=destination] [/allowFullOS]
Key
/validate Instruct MBR2GPT.exe to perform only the disk validation steps and report whether
the disk is eligible for conversion.
/convert Instruct MBR2GPT.exe to perform the disk validation and to proceed with the conversion if
all validation tests pass.
/disk:diskNumber 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 used by the
diskpart.exe tool SELECT DISK SYSTEM command.
/logs:logDirectory
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 other partition type mappings between MBR and GPT.
The MBR partition number is specified in decimal notation, not hexadecimal.
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's run from Windows PE.
This option overrides this block and enables disk conversion while running in the full
Windows environment.
Note: Since the existing MBR system partition is in use while running the full Windows environment, it can't be reused. In this case, a new ESP is created by shrinking the OS partition.
To use this tool in a deployment task sequence with Configuration Manager or Microsoft Deployment Toolkit (MDT), you must first update the Windows PE image (winpe.wim, boot.wim) with the Windows ADK 1703, or a later version.
The conversion tool will attempt to remap all drive letter assignment information contained in the registry that corresponds to the volumes of the converted disk. If a drive letter assignment can't be restored, an error will be displayed at the console and in the log, so that you can manually perform the correct assignment of the drive letter.
Four log files are created by MBR2GPT:
diagerr.xml
diagwrn.xml
setupact.log
setuperr.logThese files contain errors and warnings encountered during disk validation and conversion. Information in these files can be helpful in diagnosing problems with the tool. The setupact.log and setuperr.log files will have the most detailed information about disk layouts, processes, and other information pertaining to disk validation and conversion.
The setupact*.log files are different than the Windows Setup files that are found in the %Windir%\Panther directory.
The default location for all these log files in Windows PE is %windir%.
Return code Description 0 Conversion completed successfully. 1 Conversion was canceled by the user. 2 Conversion failed due to an internal error. 3 Conversion failed due to an initialization error. 4 Conversion failed due to invalid command-line parameters. 5 Conversion failed due to error reading the geometry and layout of the selected disk. 6 Conversion failed because one or more volumes on the disk is encrypted. 7 Conversion failed because the geometry and layout of the selected disk don't meet requirements. 8 Conversion failed due to error while creating the EFI system partition. 9 Conversion failed due to error installing boot files. 10 Conversion failed due to error while applying GPT layout. 100 Conversion to GPT layout succeeded, but some boot configuration data entries couldn't be restored.
disk 0 is validated for conversion. Errors and warnings are logged to the default location of %windir%.
C:\> mbr2gpt.exe /validate /disk:0 MBR2GPT: Attempting to validate disk 0 MBR2GPT: Retrieving layout of disk MBR2GPT: Validating layout, disk sector size is: 512 MBR2GPT: Validation completed successfully
Determine the partition type & disk number:
PS C:\> Get-Disk | ft -Auto Number Friendly Name Serial Number HealthStatus OperationalStatus Total Size Partition Style ------ ------------- ------------- ------------ ----------------- ---------- --------------- 0 MTFDDAK256MAM-1K1 13050928F47C Healthy Online 238.47 GB MBR 1 ST1000DM003-1ER162 Z4Y3GD8F Healthy Online 931.51 GB GPT
If Windows PowerShell and Disk Management aren't available, such as when you're using Windows PE, you can determine the partition type at a command prompt with DiskPart >list disk
Conversion example
In the following example:
As noted in the output from the MBR2GPT tool, you must make changes to the computer firmware so that the new EFI system partition will boot properly.
X:\>DiskPart.exe Microsoft DiskPart version 10.0.15048.0 Copyright (C) Microsoft Corporation. On computer: MININT-K71F13N DISKPART> list volume Volume ### Ltr Label Fs Type Size Status Info ---------- --- ----------- ----- ---------- ------- --------- -------- Volume 0 F CENA_X64FRE UDF DVD-ROM 4027 MB Healthy Volume 1 C System Rese NTFS Partition 499 MB Healthy Volume 2 D Windows NTFS Partition 58 GB Healthy Volume 3 E Recovery NTFS Partition 612 MB Healthy Hidden DISKPART> select volume 2 Volume 2 is the selected volume. DISKPART> list partition Partition ### Type Size Offset ------------- ---------------- ------- ------- Partition 1 Primary 499 MB 1024 KB * Partition 2 Primary 58 GB 500 MB Partition 3 Recovery 612 MB 59 GB DISKPART> detail partition Partition 2 Type : 07 Hidden: No Active: No Offset in Bytes: 524288000 Volume ### Ltr Label Fs Type Size Status Info ---------- --- ----------- ----- ---------- ------- --------- -------- * Volume 2 D Windows NTFS Partition 58 GB Healthy DISKPART> exit Leaving DiskPart... X:\> mbr2gpt /convert /disk:0 MBR2GPT will now attempt to convert disk 0. If conversion is successful the disk can only be booted in GPT mode. These changes cannot be undone! MBR2GPT: Attempting to convert disk 0 MBR2GPT: Retrieving layout of disk MBR2GPT: Validating layout, disk sector size is: 512 bytes MBR2GPT: Trying to shrink the system partition MBR2GPT: Trying to shrink the OS partition MBR2GPT: Creating the EFI system partition MBR2GPT: Installing the new boot files MBR2GPT: Performing the layout conversion MBR2GPT: Migrating default boot entry MBR2GPT: Adding recovery boot entry MBR2GPT: Fixing drive letter mapping MBR2GPT: Conversion completed successfully MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode! X:\>DiskPart Microsoft DiskPart version 10.0.15048.0 Copyright (C) Microsoft Corporation. On computer: MININT-K71F13N DISKPART> list disk Disk ### Status Size Free Dyn Gpt -------- ------------- ------- ------- --- --- Disk 0 Online 60 GB 0 B * DISKPART> select disk 0 Disk 0 is now the selected disk. DISKPART> list volume Volume ### Ltr Label Fs Type Size Status Info ---------- --- ----------- ----- ---------- ------- --------- -------- Volume 0 F CENA_X64FRE UDF DVD-ROM 4027 MB Healthy Volume 1 D Windows NTFS Partition 58 GB Healthy Volume 2 C System Rese NTFS Partition 499 MB Healthy Hidden Volume 3 FAT32 Partition 100 MB Healthy Hidden Volume 4 E Recovery NTFS Partition 612 MB Healthy Hidden DISKPART> select volume 1 Volume 1 is the selected volume. DISKPART> list partition Partition ### Type Size Offset ------------- ---------------- ------- ------- Partition 1 Recovery 499 MB 1024 KB * Partition 2 Primary 58 GB 500 MB Partition 4 System 100 MB 59 GB Partition 3 Recovery 612 MB 59 GB DISKPART> detail partition Partition 2 Type : ebd0a0a2-b9e5-4433-87c0-68b6b72699c7 Hidden : No Required: No Attrib : 0000000000000000 Offset in Bytes: 524288000 Volume ### Ltr Label Fs Type Size Status Info ---------- --- ----------- ----- ---------- ------- --------- -------- * Volume 1 D Windows NTFS Partition 58 GB Healthy
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YouTube walkthrough - Convert BIOS / MBR to UEFI / GPT without reformatting - MBR2GPT tool.