Windows 8 and 8.1 Forums

Cannot install to MBR (non UEFI) disks

  1. #1

    Posts : 39
    Windows 8.1 Update 1 64bit Pro

    Cannot install to MBR (non UEFI) disks

    So I have a sata hdd in laptop, no other hdd's.

    Booted of usb install media.

    Problem is this.

    When creating partition instead of auto creating the extra hidden partition it just makes to main windows partition, and then will refuse to install.

    I also had another USB install media, from same iso, that would refuse to create GPT partitions, but works fine with MBR. Something is odd with the windows 8 installer. That usb media I cannot use now as I recreated it with GPT which made it work to create secureboot compatible partitions.

    This is the error "we couldnt create a new partition or locate an existing one"

      My System SpecsSystem Spec

  2. #2

    Posts : 2,613
    Windows 3.1 > Windows 10

    The USB has to be formatted Fat32
    Then copy the contents of the ISO to the USB

    Once you get the partition screen - delete all the partitions - and allow windows to install to the unallocated space and create the partitions...

    The partitions are created based on how the PC was booted...
    If you booted the USB in Legacy mode - the partitions will be created in MBR format
    If you booted the USB in UEFI mode - the partitions will be created in GPT format

    If the PC supports UEFI booting you must enable that support, and then use the (F12 usually) Boot Menu Options to select the UEFI USB
    otherwise most older PC's will automatically boot MBR..

    Most Newer PC's will require Legacy Support to be enabled, before the PC will boot into MBR mode
    Otherwise it will boot UEFI

    If both UEFI and Legacy support are enabled - by default the PC will boot into MBR/Legacy Supported mode
    So you must use the Boot Menu Options to select the UEFI Boot Device
      My System SpecsSystem Spec

  3. #3

    Posts : 39
    Windows 8.1 Update 1 64bit Pro

    thanks, it seems microsoft have coded in automatic systems with no manual overide I assume to be dumb proof but I consider not giving the admin control anti intuitive.

    The issue was down to how the system was booting, your reply is indeed correct on both accounts (so thank you), I found a post on microsoft technet forums where a clever guy found the issue that I had with it refusing to install MBR on old laptop.

    The MBR refuse to install problem. Is if one uses a usb3 stick in a usb2 port, the installer will refuse to continue past the partition screen. There is some very weird quircks in this windows installer (we all know the one where it gets confused as well with more than one hdd connected).

    So conclusion?

    To support UEFI/GPT setup I had to split my install.wim into two install.swm files so they fit onto FAT32. Really odd that the new UEFI standard has no support for exFAT a modern version of FAT.
    On my old laptop and testing PC (which both are not UEFI and also both dont have usb3 ports), I have to use a slow usb stick because all my fast ones are usb3 sticks.

    Oddly on this PC when I installed win8, I was able to install; GPT when using a MBR install media, I think thats because the bios was configured as GPT enabled but has an overide boot function to allow to boot of MBR media whilst in GPT mode, my new laptop also handles this, where the bios is set to GPT preferred or MBR preferred, but this prevents the correct behaviour from the windows installer.
      My System SpecsSystem Spec

Cannot install to MBR (non UEFI) disks

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