1.    09 Jun 2017 #1
    Join Date : Jun 2017
    Posts : 3
    Windows 10 Pro 64-bit v1703

    HDD not listed in UEFI mode even after GPT conversion.


    Hello everybody,

    i need help with something.I was using the legacy bios mode (MBR) for a long time now but i wanted to switch to UEFI mode so i used mbr2gbt.exe to convert my hdd to GPT after the conversion was complete it said on the black screen that i had to change my boot mode to UEFI in order to boot into windows 10 so i restarded my computer and entered the bios and i changed my boot mode from LEGACY+UEFI to UEFI then i saved everything and rebooted my pc but for some reason it doesn't boot to windows it boots to EFI Shell and both my Hard Disk and my DVD-RW are missing from the boot priority list.Please i need assistance with this situation

    Thank You

    By the way I'm from Turkey so sorry for bad english
      My ComputerSystem Spec
  2.    09 Jun 2017 #2
    Join Date : Jan 2015
    UK, Midlands
    Posts : 10,968
    Win 10 Pro (1703)

    Hi, the Windows partition layout for an EFI booting system is quite different to that for one using legacy BIOS.

    The first has 4 partitions, the second, 3.
    BIOS/MBR-based hard drive partitions | Microsoft Docs
    UEFI/GPT-based hard drive partitions | Microsoft Docs

    A legacy BIOS cannot boot an OS on a GPT disk.

    Thus your disk is unbootable as you've found.

    Now I could tell you how to take a valid Windows partition from one GPT disk to another and create a bootable system.
    What I don't know whether that would work with a Windows partition created under legacy BIOS.

    I'll be interested to see what others suggest as I don't want to play guessing games.

    How big is your disk?
    Do you have a backup or disk image of your original BIOS disk?
      My ComputerSystem Spec
  3.    09 Jun 2017 #3
    Join Date : Jun 2017
    Posts : 3
    Windows 10 Pro 64-bit v1703
    Thread Starter

    1.Size of the hdd is 1TB
    2.I don't have backup of bios
      My ComputerSystem Spec
  4.    09 Jun 2017 #4
    Join Date : Jun 2016
    Los Angeles
    Posts : 1,031
    Windows 10 Pro

    Try changing it back to Legacy+UEFI. If that fails,
    I would start fresh reinitialize the drive GPT and Install Windows with the GPT+UEFI option. Loosing all data.

    Change the Bios to Legacy,
    Boot off of Windows install Media, choose your Language and press Shift+F10 to go directly to the Command Prompt.
    Here type Diskpart and press enter. At this prompt type the following Bold commands and press enter after each one
    ii) list disk
    (ie) DISKPART > list disk
    It now lists disk by number
    you have to select the disk next with
    iii) select disk <disk number>
    (ie) DISKPART> Select Disk (disk number) = as listed in previous command. The selected disk now has an Asterisk next to it.
    iv) clean (this erases all data on the Disk, so be sure you choose the correct one)
    (ie) DISKPART> clean
    v) convert gpt
    vi) create partition primary
    vii) format fs=ntfs quick
    now for verification of disk status and free space type
    v) list disk
    the status should be "online" and free space should be "disk size"
    ‘vi)exit
    Remove install media, Shut down computer
    On another computer, if you have a Windows ISO image, create a bootable GPT/UEFI USB Windows installer with Rufus. Be sure to change Partition Scheme to GPT for UEFI.
    Put the USB Flash drive in the troubled computer, boot into Setup (Bios) change Boot mode to UEFI Restart the computer and go back to the Bios Boot Tab, the Flash Drive should now be listed as bootable media, move this to First Boot Device, Save and Exit.
      My ComputerSystem Spec
  5.    09 Jun 2017 #5
    Join Date : Jun 2017
    Posts : 3
    Windows 10 Pro 64-bit v1703
    Thread Starter

    Quote Originally Posted by spunk View Post
    Try changing it back to Legacy+UEFI. If that fails,
    I would start fresh reinitialize the drive GPT and Install Windows with the GPT+UEFI option. Loosing all data.

    Change the Bios to Legacy,
    Boot off of Windows install Media, choose your Language and press Shift+F10 to go directly to the Command Prompt.
    Here type Diskpart and press enter. At this prompt type the following Bold commands and press enter after each one
    ii) list disk
    (ie) DISKPART > list disk
    It now lists disk by number
    you have to select the disk next with
    iii) select disk <disk number>
    (ie) DISKPART> Select Disk (disk number) = as listed in previous command. The selected disk now has an Asterisk next to it.
    iv) clean (this erases all data on the Disk, so be sure you choose the correct one)
    (ie) DISKPART> clean
    v) convert gpt
    vi) create partition primary
    vii) format fs=ntfs quick
    now for verification of disk status and free space type
    v) list disk
    the status should be "online" and free space should be "disk size"
    ‘vi)exit
    Remove install media, Shut down computer
    On another computer, if you have a Windows ISO image, create a bootable GPT/UEFI USB Windows installer with Rufus. Be sure to change Partition Scheme to GPT for UEFI.
    Put the USB Flash drive in the troubled computer, boot into Setup (Bios) change Boot mode to UEFI Restart the computer and go back to the Bios Boot Tab, the Flash Drive should now be listed as bootable media, move this to First Boot Device, Save and Exit.
    Thank you so much <3 it worked Thank you all for all the assistance
      My ComputerSystem Spec

 


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