Windows 8 and 8.1 Forums


Re-explanation, help, converting MBR to GPT (non system)

  1. #1

    Re-explanation, help, converting MBR to GPT (non system)


    Hello all

    Let me say this is a nice community with a good lot of resources to get drunk on at times in need or when finding those spare moments to work brain cells

    First I will inform you that I have scoured this forum and many many other resources as to my seemingly simple issue in which I must be missing some small detail to which has sidelined my progress.

    Situation:

    I have external drives greater than 3+ TB in size with data I wish to keep. Because they were external and using their own firmware/controller, they were using MBR as you may know. I have since ripped them out and placed them in my rig for purposes of better speed and heat dissipation. Of course, windows will not show these drives in explorer alone. I have read up on using the mini tool PA in order to convert. Seems simple, but when doing so (selecting drive and then selecting/applying convert to GPT) and then even rebooting, there is no change, not showing in explorer. These drives were one disk, not partitioned previously or at all. What simple step am I missing here? I would appreciate a point in the right direction. Because of the reason of data, I have been apt to go ahead and "try" anything further before seeking any further help.

    Let me itterate that this is not an issue of anything being corrupted by a power failure or otherwise. If I stick the drive back onto the external controller, while MBR, it appears and works, no problem (thats after i toggle back to MBR from GPT convert, of course).

    Windows 8.1 x64, system drive as MBR currently

    Click image for larger version

    Thanks for clicking the thread, any help is surely appreciated Apologies as I know and have read the MBR/GPT threads and tutorials, but something just isnt clicking right... or maybe due to fear of clicking further as to possibly losing data is more like it, without being sure of the further click itself.

      My System SpecsSystem Spec

  2. #2


    Posts : 2,690
    Windows 3.1 > Windows 10


    Your current systems disk (windows disk) is MBR ???

    Disk 4 MBR - shows unformatted and unallocated space..

    With all disks install inside PC open a command prompt(admin)

    Type> diskpart
    type> list disk
    type> list volume

    post a pic of cmd window
      My System SpecsSystem Spec

  3. #3


    Your SATA ports need to be set to AHCI also are you sure that your Motherboard support UEFI GPT
      My System SpecsSystem Spec

  4. #4


    Hiya KYHI

    Yes, system disk is MBR. FYI am in planning/backup stage of wiping sys disk and starting fresh and installing as GPT.

    current snapshot of guts

    Click image for larger version
      My System SpecsSystem Spec

  5. #5


    Quote Originally Posted by Clintlgm View Post
    Your SATA ports need to be set to AHCI also are you sure that your Motherboard support UEFI GPT
    Yes. Sabretooth 990FX Gen 2.0. A bit confused as this install was a bit of a rush and time has gone by since I set it up. Yet after re-examining the sys drive, there is an efi part on that disk. This bios has setting to run normal bios or UEFI/bios. I believe the latter setting acts as a hybrid. As to why it shows sys drive as MBR is a bit puzzling and my memory of actions taken for initial install have slipped away. Currently prepping for a wipe/install due to 2 other drives (data) starting to fail and some registry issues I have came across in which I dont have the time for nowadays to suss out any further than what I have, small issues, but nags. Another issue that has become perplexing was noticing memtest reporting my 12800 mem running @800 instead of 1600 (as bios reports 1600). But one issue at a time ya know

    The rush install was due to the last pc being hobbled on last leg after many years and finally "dying" on me, and me giving up on using more duct tape while needing a reliable pc for work related tasks
      My System SpecsSystem Spec

  6. #6


    Posts : 2,690
    Windows 3.1 > Windows 10


    Disk 1 and Disk 2 are listed as GPT and the information about volume 6 and 7 shows as raw data..

    If you can read that data via external drive - then save it to one of your many drives.. Even if you have to convert them back to MBR

    Your System does not have an EFI partition - but has a 350MB Recovery Tools partition - on a MBR Disk

    I have 2 internal disks and both are GPT (win8.1 x64) I can access external MBR and GPT disks -

    But seen to remember needing to have one or the other, as internal disks,
    Disk not initialize error - I believe
      My System SpecsSystem Spec

  7. #7


    ok... well, your answer was of my last resort resolution. Is it not possible to convert the external MBR drive to GPT after placing internally while not losing data? Basically rebuilding/converting the MBR to GPT and then making the raw data partiton visible within windows/explorer? This was my impression after reading through the many threads and sources for this issues, sort of a presto-change-o. Am i under the wrong impression?
      My System SpecsSystem Spec

  8. #8


    Posts : 2,690
    Windows 3.1 > Windows 10


    You can place your external MBR disk - along side your other internal MBR disks..

    Converting it to GPT caused - a RAW / Unformated Partition > which may no longer be readable
      My System SpecsSystem Spec

  9. #9


    Quote Originally Posted by KYHI View Post
    You can place your external MBR disk - along side your other internal MBR disks..

    Converting it to GPT caused - a RAW / Unformated Partition > which may no longer be readable
    Not sure what you mean by placing external along side the internal, thats what I'm trying to do, but as you can see, its not possible. I'm trying to find out how to do so while I have read other threads that report this as a simple thing to do. Basically, like the old days, rebuilding an MBR. Only in this case I'm not rebuilding the MBR, i'm wanting and having to convert the MBR to GPT to be able to view the disk as a single partition due to the size of that partition/disk. As you see in the first post snapshot, one disk was toggled to GPT/RAW (by means of PA) while the other is still MBR/RAW, cant view either in explorer. This was why I took that snapshot as a comparision of 2 disks after toggling one of them with PA to a "convert" disk to GPR. In this scenario, i can go back to Disk 2 in PA and "undo" the GPT, converting back to MBR, then place that drive on the external controller and read it as normal through explorer. The problem seems to lie within the controller on the MB not reading that same disk 2 after **supposedly** converting from MBR to GPT. Both of those drives in that snapshot are both on the internal sata conroller (AMD SB950). Drive 2 having the action taken of PA "converting" that disk, supposedly, to GPT and not touching Disk 3. But obviously diskpart doesnt see it that way. In the diskpart shot, the GPT drive is a seperate different 5TB drive/disk (no data on it) in which I used windows disk manager, i believe, to format to GPT.

    Attaching disk management screen shot to further show the 3 drives. Disk 0 being the sys, Disk 1 being the "new" drive I formatted (no data) to GPT, Disk2 being the external drive from post #1 that was toggled to convert GPT, and Disk3 being another external that was left untouched. And keep in mind that both 2 & 3 were/are currently, on the internal controller.

    Click image for larger version
      My System SpecsSystem Spec

  10. #10


    Posts : 2,690
    Windows 3.1 > Windows 10


    The organization of the partition table in the MBR limits the maximum addressable storage space of a disk to 2 TB

    Therefore, the MBR-based partitioning scheme is in the process of being superseded by the GUID Partition Table (GPT) scheme in new computers.

    A GPT Disk can coexist with a MBR Disk in order to provide some limited form of a backwards compatibility for older systems.

    Your Host system is the older Legacy MBR and you are looking to support the newer GPT within your host
    If possible convert Host OS to UEFI-GPT and then you will have the support needed for 5TB GPT Drives
      My System SpecsSystem Spec

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Re-explanation, help, converting MBR to GPT (non system)
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