1. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #1

    Dual boot win7/win10 MBR/UEFI problem, cannot reinstall Win 10 ISO


    I've been an insider since FEB. Last ISO I installed was 10074. Since updating to 10240/rtm things have gotten buggy, apps don't function, can't update etc.

    I want to install the latest ISO on the 10240 oartition, but when I try I get, "Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks."

    The solution is to adjust those boot parameters in the BIOS, make everything legacy/MBR, so I've read. Problem is, the bios is locked down, it's a HP Envy laptop. The BIOS supports both MBR and GPT, however, GPT is the default, and legacy boot options only kick in when GPT is not supported. There is no way to change this. So, I have MBR for recovery and Win 7 partitions, and selecting any partition installing Win 10 gives me this error.

    Is there a work around?

    (I can not reset because of the inaccessible boot device bug, maybe related, besides I need the ability to reformat that partition being an insider)

    It's really frustrating as up until build 1074, this was not an issue.
      My System SpecsSystem Spec


  2. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #2

    I'm thinking reinstall build 10074, and then try to update, but this does not really help going forward. Is there a a non destructive way to make my Win 7 partition GPT?
      My System SpecsSystem Spec


  3. Joined : Oct 2014
    Posts : 107
    Windows 10
       04 Aug 2015 #3

    mrpumpkin said: View Post
    I want to install the latest ISO on the 10240 oartition, but when I try I get, "Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks."
    - Delete all partitions on the disk, so you can use GPT (GUID Partition Table).
    - But if you want to use MBR (Master Boot Record) partition table, then boot from the Windows installation media in Legacy BIOS Boot Mode.

    Quote from this post: UEFI Boot Mode (installing using the GPT partition style) and Legacy BIOS Boot Mode (installing using the MBR partition style). -> link

    Tip   Tip
    Error message when you boot from the Windows installation media in Legacy BIOS Boot Mode:

    Windows cannot be installed to this disk. The selected disk is of the GPT partition style. (see screenshot below)

    That is because Windows can only be installed to MBR disk in Legacy BIOS Boot Mode, but you plan to install Windows on a GPT disk.

    - Boot from the Windows installation media in UEFI Boot Mode, so you can use GPT (GUID Partition Table).
    - But if you want to use MBR (Master Boot Record) partition table, then delete all partitions on the disk.

    Click image for larger version. 

Name:	Windows cannot be installed to this disk. The selected disk is of the GPT partition style.png 
Views:	42 
Size:	37.4 KB 
ID:	44050

    Error message when you boot from the Windows installation media in UEFI Boot Mode:

    Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks. (see screenshot below)

    That is because Windows can only be installed to GPT disk in UEFI Boot Mode, but you plan to install Windows on an MBR disk.

    - Delete all partitions on the disk, so you can use GPT (GUID Partition Table).
    - But if you want to use MBR (Master Boot Record) partition table, then boot from the Windows installation media in Legacy BIOS Boot Mode.

    Click image for larger version. 

Name:	Windows cannot be installed on this disk. The selected disk has an MBR partition table.png 
Views:	42 
Size:	36.1 KB 
ID:	44051
    Last edited by genet; 13 Nov 2015 at 13:08.
      My System SpecsSystem Spec


  4. Joined : Jun 2015
    Posts : 1,602
    Windows 3.1 to Windows 10
       04 Aug 2015 #4

    to force boot in MBR mode rename "bootmgr.efi" to "bootmgr.efi.old"

    you can also rename the "EFI" folder to "EFI.old"

    this will sort of disable the setup media's UEFI booting
      My System SpecsSystem Spec


  5. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #5

    Kyhi said: View Post
    to force boot in MBR mode rename "bootmgr.efi" to "bootmgr.efi.old"

    you can also rename the "EFI" folder to "EFI.old"

    this will sort of disable the setup media's UEFI booting
    Where would I do this?
      My System SpecsSystem Spec


  6. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #6

    genet said: View Post
    - Delete all partitions on the disk, so you can use GPT (GUID Partition Table).
    - But if you want to use MBR (Master Boot Record) partition table, then boot in Legacy BIOS Boot Mode.

    Here is info about UEFI Boot Mode (installing using the GPT partition style) and Legacy BIOS Boot Mode (installing using the MBR partition style). -> link
    I was wanting to save the Win 7 partition, but even if I nixed it and everything went to hell, would I be able to reformat using HP recovery media? Or would I end up not being able to boot their discs because the HD was converted? It's an OEM license and software.
      My System SpecsSystem Spec


  7. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #7

    Kyhi said: View Post
    to force boot in MBR mode rename "bootmgr.efi" to "bootmgr.efi.old"

    you can also rename the "EFI" folder to "EFI.old"

    this will sort of disable the setup media's UEFI booting
    Found it, but I'm in my win 10 partition with admin privileges, but renaming is not an option. Would it be in Win 7?
      My System SpecsSystem Spec


  8. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       04 Aug 2015 #8

    I was able to rename the "bootmgr.efi" to" bootmgr.efi.old" in the ISO after rebooting to win 7 (this alone is a cause of concern). But it did not work, at least for me.
      My System SpecsSystem Spec


  9. Joined : Aug 2015
    Posts : 142
    dual boot win10/win7
       05 Aug 2015 #9

    I created a new USB using an older USB 2 only drive. It then appeared in the boot manager with both MBR and UEFI options for booting, and I was able to install using the MBR option. The other drive did not give me the MBR/legacy option.
      My System SpecsSystem Spec


 


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