Convert Windows 10 from Legacy BIOS to UEFI without Data Loss  

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  1. ntd252's Avatar
    Posts : 24
    Windows 7/Windows 10 1803 Dual boot
       #90

    Brink said: View Post
    Hello ntd252,

    I wouldn't recommend doing this when you have a multiboot system like that. It will most likely break it.
    Is there any way to do it quicly?
    In the past, I installed Windows 7 first with a 100MB System Reserved, then Windows 10 and last Linux Mint.
    Linux uses Grub2, while Windows7/10 use Windows boot manager.
    I will be sad if I have to copy everything from current disk, convert it and then get data back.
      My ComputerSystem Spec

  2. Brink's Avatar
    Posts : 36,955
    64-bit Windows 10 Pro build 18860
    Thread Starter
       #91

    Not that I'm aware of.

    You might create a separate thread in the Installation & Upgrade forum area to see if someone may know an easier way.
      My ComputersSystem Spec

  3. bayustev's Avatar
    Posts : 71
    Windows10 pro x64,Version 1803
       #92

    halo, can i reverse from uefi boot to legacy ? thanks
      My ComputersSystem Spec

  4. Brink's Avatar
    Posts : 36,955
    64-bit Windows 10 Pro build 18860
    Thread Starter
       #93

    Currently, that requires a clean install.
      My ComputersSystem Spec

  5.    #94

    bayustev said: View Post
    halo, can i reverse from uefi boot to legacy ? thanks

    Brink said: View Post
    Currently, that requires a clean install.
    I must disagree, @Brink. The user can create a backup image of the Windows partition. Then they can manually setup the HDD/SDD with MBR format partitioning for legacy BIOS booting using a couple of different methods - manually with diskpart commands or a boot drive containing partitioning software such as Kyhi's recovery drive. Restore the Windows partition from the backup image and recreate the legacy BIOS boot files using the bcdboot command.
      My ComputerSystem Spec

  6. Brink's Avatar
    Posts : 36,955
    64-bit Windows 10 Pro build 18860
    Thread Starter
       #95

    That's good to hear, but not something for the average bear.
      My ComputersSystem Spec

  7.    #96

    Brink said: View Post
    That's good to hear, but not something for the average bear.
    I would say the average bear could do it, but a newbie would struggle.

    I will prepare a guide which could be whipped up into a tutorial.

    I have the basics in the guide I wrote to update small storage tablets.
      My ComputerSystem Spec

  8.    #97

    When I run
    mbr2gpt /convert /allowfullOS this happens:

    Code:
    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
    Disk layout validation failed for disk 0
    MBR2GPT: Conversion failed
    Any idea on how to fix this
      My ComputerSystem Spec

  9. Brink's Avatar
    Posts : 36,955
    64-bit Windows 10 Pro build 18860
    Thread Starter
       #98

    Hello slamdunk, and welcome to Ten Forums.

    What does it report when running the command below?

    mbr2gpt /validate
      My ComputersSystem Spec

  10.    #99

    Brink said: View Post
    Hello slamdunk, and welcome to Ten Forums.

    What does it report when running the command below?

    mbr2gpt /validate
    Thanks.
    I get this

    Code:
    C:\WINDOWS\system32>mbr2gpt /validate
    ERROR: MBR2GPT can only be used from the Windows Preinstallation Environment. Use /allowFullOS to override.
    
    C:\WINDOWS\system32>mbr2gpt /validate /allowFullOS
    MBR2GPT: Attempting to validate disk 0
    MBR2GPT: Retrieving layout of disk
    MBR2GPT: Validating layout, disk sector size is: 512 bytes
    Disk layout validation failed for disk 0
    EDIT: Never mind. I had 4 partitions then I deleted an unused one now it works.
      My ComputerSystem Spec


 
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