[Solved] How to boot Windows 7 64 UEFI with second MBR disk attached

Discussion in 'Windows 7' started by patkim, Mar 21, 2017.

  1. patkim

    patkim MDL Novice

    Sep 26, 2016
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  2. BigReds

    BigReds MDL Novice

    Apr 24, 2015
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    The issue is your uefi drive is setup as default boot drive and is why Windows setup won't install mbr on other drive.
    The safest solution is to disable uefi drive in bios and set your mbr drive as default then install Windows as you normally would.
    Once done you can enable uefi drive again and make whichever drive default you want to always boot and just use the bios boot menu to choose what drive you want to boot first.
     
  3. patkim

    patkim MDL Novice

    Sep 26, 2016
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    May be I should have mentioned that I am not trying to install Windows 7 on the other MBR drive.
    That drive is just added as a second drive to my PC which already has Windows 7 64 in UEFI mode installed on first disk.

    However with this setup i.e. with an MBR disk attached as another data drive to already UEFI Windows 7, system fails to boot.

    So the setup is now
    Windows 7 64 UEFI on GPT Disk (Disk1)
    An MBR disk attached as data disk and simply to be used as a data disk (Disk2)
     
  4. Tito

    Tito Super Mod / Adviser
    Staff Member

    Nov 30, 2009
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    @patkim

    Which mobo/laptop is it?
     
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  5. BigReds

    BigReds MDL Novice

    Apr 24, 2015
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    try disabling the mbr disk and see if uefi os boots fine.
    if it does try and check if the bios has an option on which mode gets boot first by default UEFI or MBR.
    other option might be deleting mbr disk to raw to clear mbr bootsector then reboot to see if uefi os boots fine then add new partitions in windows disk management.

    windows supports gpt boot and 2nd mbr data disk, so there shouldn't be any problem getting it to work on the OS side of things.
     
  6. patkim

    patkim MDL Novice

    Sep 26, 2016
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    I don't know why it behaved like that but finally converting that MBR disk to GPT solved the issue.
    Now Windows 7 64 boots fine in UEFI mode. I have old Gigabyte motherboard so it might have earlier buggy UEFI firmware possibly.