Diskpart question-convert from GPT to MBR on a flash drive

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  1. Posts : 17,252
    Windows 11 Pro
       #11

    What really matters is if the OP wants a USB flash drive that is MBR partitioned, FAT32, and marked as active so it is universal and can be booted in either UEFI or legacy BIOS mode, there is absolutely nothing wrong with that. Or even if the OP doesn't want it to be bootable and just wants it to be MBR partitioned, there is absolutely nothing wrong with that. And if the OP wants to use diskpart to do it with, there is absolutely nothing wrong with that. Maybe we should focus on helping people achieve their desired outcomes.

    Maybe a warning that converting a drive from GPT to MBR (or MBR to GPT) using diskpart will erase whatever is on that drive might be appropriate, but I think the OP already knows that in this case.
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  2. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #12

    NavyLCDR said:
    Yes they do. During the bootable drive creation procedure, just insert "convert mbr" after the clean command. Although I am 99% certain the clean command reverts the drive back to MBR automatically anyway. In diskpart, run the "list disk" command at any time and it will tell you which drives are GPT or not.
    Thanks for clarifying that for me
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  3. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #13

    NavyLCDR said:
    Maybe a warning that converting a drive from GPT to MBR (or MBR to GPT) using diskpart will erase whatever is on that drive might be appropriate, but I think the OP already knows that in this case.
    Yeah..You're right...I knew that everything will be wiped from the drive If I'm correct the clean command would have wiped the drive completely. Then, the convert mbr creates the MBR partition table
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  4. Posts : 17,252
    Windows 11 Pro
       #14

    sportsfan148 said:
    Yeah..You're right...I knew that everything will be wiped from the drive If I'm correct the clean command would have wiped the drive completely. Then, the convert mbr creates the MBR partition table
    I'm 99% certain the clean command also creates the MBR partition table, making convert mbr unnecessary after a clean command. But it's like "assign" and "select part 1" - should not be needed, but won't hurt anything if you add it.
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  5. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #15

    NavyLCDR said:
    I'm 99% certain the clean command also creates the MBR partition table, making convert mbr unnecessary after a clean command. But it's like "assign" and "select part 1" - should not be needed, but won't hurt anything if you add it.
    Yeah...We've had the assign and select partition 1 conversation before when you explained how that works to me. Like you said though it does no harm if you want to add them
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  6. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #16

    I know that I can convert a USB flash drive to MBR from GPT using diskpart, clean and convert mbr. That's been explained to me above.
    Ive found a tutorial on Tenforums that also shows this method.
    Just out of curiosity this tutorial also shows how it can be done in Disk Management by deleting all the volumes on the disk then right clicking and selecting convert mbr. That convert mbr or convert gpt is not available. Its not greyed out or anything..its not there as an option at all. Does anybody have any idea why the option is missing in Disk Management? Ive got Fall Creators Update and my system is Windows 10 installed in UEFI.
    I know its not a problem because I can convert to MBR in Diskpart. I'm just curious as to why the Disk Management method isn't available on my laptop and apparently it is supposed to be
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  7. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #17

    NavyLCDR said:
    Yes they do. During the bootable drive creation procedure, just insert "convert mbr" after the clean command. Although I am 99% certain the clean command reverts the drive back to MBR automatically anyway. In diskpart, run the "list disk" command at any time and it will tell you which drives are GPT or not.
    Just had a thought.. if you just insert "convert mbr" after the clean command during the bootable drive creation procedure. Would it be necessary to close down the diskpart command prompt screen after the convert mbr command as the next command would be create partition primary? I thought Id better ask in case the create partition primary command causes a problem with the convert mbr command with you saying that you are 99% certain the clean command reverts the drive back to MBR automatically anyway. Would it be better to close down diskpart after clean and convert mbr. Then open diskpart up again and create partition primary, fs=fat32 quick, active, exit to finish off creating the bootable flash drive?
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  8. Posts : 17,252
    Windows 11 Pro
       #18

    sportsfan148 said:
    Just had a thought.. if you just insert "convert mbr" after the clean command during the bootable drive creation procedure. Would it be necessary to close down the diskpart command prompt screen after the convert mbr command as the next command would be create partition primary? I thought Id better ask in case the create partition primary command causes a problem with the convert mbr command with you saying that you are 99% certain the clean command reverts the drive back to MBR automatically anyway. Would it be better to close down diskpart after clean and convert mbr. Then open diskpart up again and create partition primary, fs=fat32 quick, active, exit to finish off creating the bootable flash drive?
    @sportsfan148,

    You are overthinking this way too much. I've created a bootable USB flash drive hundreds of times with different versions of Windows. Insert the USB flash drive, open a command prompt (admin), run:

    diskpart
    list disk
    select disk # <-replace # with the actual number of the USB flash drive
    clean
    create part pri
    format fs=fat32 quick
    active
    exit
    exit

    Mount the ISO file. Copy files and folders.

    Really - that's all you have to do.
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  9. Posts : 985
    Windows 10 Home 21H1
    Thread Starter
       #19

    NavyLCDR said:
    @sportsfan148,

    You are overthinking this way too much. I've created a bootable USB flash drive hundreds of times with different versions of Windows. Insert the USB flash drive, open a command prompt (admin), run:

    diskpart
    list disk
    select disk # <-replace # with the actual number of the USB flash drive
    clean
    create part pri
    format fs=fat32 quick
    active
    exit
    exit

    Mount the ISO file. Copy files and folders.

    Really - that's all you have to do.
    Yeah ..I have those instructions written down exactly as you've typed them. My question was concerning where you said to insert the convert mbr command immediately after the clean command to ensure an MBR partition had indeed been created (because at the moment my flash drive is GPT partition style). I wondered if that was OK to be done at the same time and just insert the convert mbr line in your procedure shown above or whether it was better to clean and convert mbr....exit diskpart...then go back in and perform your procedure for creating a bootable windows 10 USB flash drive. Can it all be done in one go?
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  10. Posts : 17,252
    Windows 11 Pro
       #20

    sportsfan148 said:
    Yeah ..I have those instructions written down exactly as you've typed them. My question was concerning where you said to insert the convert mbr command immediately after the clean command to ensure an MBR partition had indeed been created (because at the moment my flash drive is GPT partition style). I wondered if that was OK to be done at the same time and just insert the convert mbr line in your procedure shown above or whether it was better to clean and convert mbr....exit diskpart...then go back in and perform your procedure for creating a bootable windows 10 USB flash drive. Can it all be done in one go?
    If you want to insert all of the optional commands its:

    diskpart
    list disk
    select disk #
    clean
    convert mbr
    create part pri
    select part 1
    format fs=fat32 quick
    assign
    active
    exit
    exit

    Straight through. Nothing in between. No exiting diskpart in the middle. No removing or re-inserting the flash drive. No rebooting the computer. No stopping for a cigarette break. Just straight through. The optional commands are in bold. You should not need them.
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