Convert Legacy BIOS to UEFI

Stephan Pringle Thursday, April 21, 2022

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!

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Stephan Pringle

Technology Support Specialist at Sipylus
About The Author: Stephan Pringle is an Information Technology Support Specialist. He covers hardware and software and provides tips for you to troubleshoot and repair issues on your own. In his spare time, he writes articles about the State of New York on his Hackintosh and HackBook and that has helped him to become the top contributor of the New York City section of Yahoo! Answers.
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Stephan Pringle

About The Author: Stephan Pringle is an Information Technology Support Specialist. He covers hardware and software and provides tips for you to troubleshoot and repair issues on your own. In his spare time, he writes articles about the State of New York on his Hackintosh and HackBook and that has helped him to become the top contributor of the New York City section of Yahoo! Answers.

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