2TB 3 partition bootable MBR to 3 partition bootable GPT 4TB drive

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  1. Posts : 7,380
    Windows 7 HP 64
       #11

    videobruce said:
    I'll have to wait until I get the new 4TB HDD. I will experiment with setting it up as a GPT bootable.

    I partly bypass the process that creates those extra partitions that waste space. I use the 'hack' that fools that install process and loads the files into only one partition instead of three. I've never had a problem with doing it that way as I have had good images of the O/S; initial with no programs and current.
    Not on a GPT drive.
    Normally, on a GPT drive you have:
    EFI - 100M Fat32
    MSR - 16M RAW
    C: - Big NTFS
    NTFS Data partitions

    As you are converting from Legacy - MBR you probably will have
    C: - Big NTFS
    EFI - 100M Fat32
    NTFS Data partitions

    The EFI - 100M Fat32 is needed to boot as UEFI. Don't delete it or you won't boot.

    - I suggest you clone the 2T MBR drive into the 4T as a MBR drive to have a backup.
    - Detach all other drives from the MB leaving on only the 2T drive.
    - Boot from a Win 10 installation drive and at the Windows Setup screen, press Shift+F10 simultaneously to open a command line prompt and type:
    mbr2gpt /validate
    It may not validate as you don't have the System partition.
    if ok type:
    mbr2gpt /convert
    If successful, shut down, change BIOS to boot as UEFI
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  2. Posts : 128
    Win7 x64
    Thread Starter
       #12

    Again, there is only one partition in my MBR drives (including the SSB & HDD drives), there is no "EFI - 100M Fat32" partition.

    This is what I'm talking about;
    partitioning - Avoiding the pesky Windows 7 System Reserved Partition - Super User

    I'm confused about cloning a GPT drive it as a MBR drive
    Are you saying w/o those hidden additional partitions it won't boot using a GPT format? if so, that's a HUGE problem.
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  3. Posts : 16,245
    7 X64
       #13

    Are you saying w/o those hidden additional partitions it won't boot using a GPT format?
    Most bios will only search fat32 partitions for \EFI\MICROSOFT\BOOT\BOOTMGFW.EFI ( or some other .efi file)

    some bios will search ntfs partitions, but then there are problems with bcdedit unable to find the bcd store.

    If you want to boot windows in uefi mode, you want a fat32 Efi System Partition (esp) which is where the boot critical files live
    Last edited by SIW2; 4 Weeks Ago at 23:17.
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  4. Posts : 184
    Windows 7 Home Premium
       #14

    videobruce said:
    Again, there is only one partition in my MBR drives (including the SSB & HDD drives), there is no "EFI - 100M Fat32" partition.
    Why would it. An EFI System Partition is specific to GPT.

    You may not have a dedicated System partition on MBR, but you do have a System partition as otherwise you would have no boot manager. Your System partition is drive C, and it's marked as active.

    You cannot have a partition marked as active on a GPT disk, so you cannot have drive C as the System partition. Your System partition on GPT must be formatted FAT32, so it must be separate.
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  5. Posts : 128
    Win7 x64
    Thread Starter
       #15

    I was responding to SIW2 post.

    Can I get this boot/FAT32 partition (whatever it is called) without doing a full Windows installed, or is that the only way?
    If so, can I forceably stop the full install after it creates the additional partition, or won't that work? Then load my saved W7 image file?
    Or;
    If I have to go thru the entire install, can I then restore my backup image of W7 that I already have to the main partition w/o disturbing that FAT partition? (assuming all of that I described correctly)
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  6. Posts : 7,380
    Windows 7 HP 64
       #16

    On a Legacy-MBR, BIOS transfer the boot sequence to the BIOS priority boot drive MBR that will transfer to a master boot manager on an Active partition. This master boot manager (like Linux Grub) can transfer the boot sequence to a partition (like Linux) or to another boot manager in another partition (like Windows). It is a serial chain mode.
    On an UEFI-GPT, BIOS transfer the boot sequence to the BIOS priority boot manager on a Fat32 Partition and then to a OS on a partition (same drive or even to a different drive). On the FAT32 partition you may have one or many boot manager (Linux and Windows etc). It is not a serial chain mode. It is a parallel mode.

    You're seeing a problem where it isn't. Let's put this way.
    - Any drive bigger than 2.2T, normally formatted must be initialized as GPT to be able to use all available space. If it is initialized as MBR you will have a 2.2T partition and the remaining space will be set as unallocated and can't be used.
    - GPT drive can be used as data drive in Win 7, 8, 10 (32 or 64 bits) and Win 11 (64 bits)
    - GPT drive can be used as a boot able drive in Win 7, 8, 10 &11 (64 bits only )
    - A GPT drive don't have a MBR so it can't be used to boot as Legacy.

    In other words: to use the 4T drive it must be initialized as GPT and as a Win 7 boot able drive it must have a EFI -100M - FAT32 partition. On a 4T drive that is a little more than nothing
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  7. Posts : 128
    Win7 x64
    Thread Starter
       #17

    I have known and understood drives larger than 2TB have to be GPT. I have had a 4TB storage drive in the tower for a few years now. What I didn't know until now Windows needs that xtra partition which (purposely at the time) wasn't created on my 2 MBR drives (with NO issue up to now).

    If I initialize this new HDD, re-install W7 (x64) then, can I restore a MBR image I have from the existing install on the 2TB drive which will be removed? Will that work?
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  8. Posts : 7,380
    Windows 7 HP 64
       #18

    videobruce said:
    If I initialize this new HDD, re-install W7 (x64) then, can I restore a MBR image I have from the existing install on the 2TB drive which will be removed? Will that work?
    Yes you can. That is one way to convert a Legacy-MBR into a UEFI-GPT.

    - Detach all other boot able drives. It is important or Win 7 can be installed on one drive and the boot manager on another
    - Boot the Win 7 installation drive as UEFI and install Win 7 as UEFI-GPT
    - It will create 3 partitions:
    EFI - 100M Fat32
    MSR - 16M RAW
    C: - Big NTFS

    When done, boot from the other main drive
    - Delete the Win 7 partition just created. It will create a big unallocated space
    - Clone the old Win 7 partition and data partition to the unallocated space created above.

    Using Diskpart commands you can also initialize the new drive as GPT, create the EFI and the MSR partition, clone actual Win 7 and data partitions from the 2T drive and then load the boot manager on the EFI partition. It is faster then the previous option.
    I can give you the commands.
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  9. Posts : 128
    Win7 x64
    Thread Starter
       #19

    Understood about disconnecting bootable drives, I got caught probably 15 or more years ago once, with another bootable drive connected and it messed up that drive.
    When you say "Clone the old Win 7 partition" are you referring to using an image (True Image 2019 in my case) of my 2nd drives active/bootable partition? Note the attachment, Disc2 is the GPT 4TB existing drive which will stay that way after the new 4TB HDD arrives. Disc 1 is the older 2TB bootable drive that is getting replaced.
    Attached Thumbnails Attached Thumbnails 2TB 3 partition bootable MBR to 3 partition bootable GPT 4TB drive-existing-pc-drives.png  
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  10. Posts : 7,380
    Windows 7 HP 64
       #20

    I don't see the new 4T drive or it is disk 2 on your disk manager image?

    Normally a disk image program can recover a partition from a saved image or it can copy a drive partition from the source drive (2T) to the target drive (4T).
    I use to have Acronis true image but I don't remember what it was capable of. Now I have Macrium Reflect, that I like it very much, and it can just drag and drop a partition from source to target.

    Dont worry. Diskgenius (free) can clone a partition from one drive to another.
    Clone / Copy Partition with Best Cloning Software - DiskGenius

    Aomei Partition Assistant (free) can also clone a partition from one drive to another.
    Safely Copy Partition to Another New Drive in Windows 7, 8, 10, 11

    Is your Win 7 on a DVD or on a USB drive? If USB, is it Fat32 and did you add the \efi\boot folder to be able to boot as UEFI?
    Last edited by Megahertz07; 4 Weeks Ago at 13:12.
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