To convert Legacy BIOS to UEFI or MBR to GPT to meet the requirements for Windows 11, try the following.
mbr2gpt /convert /allowfullos
Note: You may need to execute bcdboot C:\Windows /s C: /f ALL if “Cannot find OS partition(s) for disk 0” is shown so it is recommended to do it beforehand.
C:\Users\Administrator>bcdboot C:\Windows /s C: /f ALL
Boot files successfully created.
C:\Users\Administrator>mbr2gpt /convert /allowfullos
MBR2GPT will now attempt to convert the default book disk.
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 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: Fixing drive letter mapping
MBR2GPT: Conversion completed successfully
Call WinReReapir to repair WinRE
MBR2GPT: Failed to update ReAgent.xml, please try to manually disable and enable WinRE.
MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!
Commands
MBR2GPT.exe /validate|convert [/disk:] [/logs:] [/map:=] [/allowFullOS]Where:
/validate
– Validates that the selected disk can be converted
without performing the actual conversion.
/convert
– Validates that the selected disk can be converted
and performs the actual conversion.
/disk:
– Specifies the disk number of the disk to be processed.
If not specified, the system disk is processed.
/logs:
– Specifies the directory for logging. By default logs
are created in the %windir% directory.
/map:=
– Specifies the GPT partition type to be used for a
given MBR partition type not recognized by Windows.
Multiple /map switches are allowed.
/allowFullOS
– Allows the tool to be used from the full Windows
environment. By default, this tool can only be used
from the Windows Preinstallation Environment.
Results
MBR2GPT will now attempt to convert the default book disk.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 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!
Stephan Pringle
