Windows 10 MBR -> GPT

Microsoft states it is not possible to convert an existing Windows 10 installation from MBR to GPT mode. Now following how to proof them they're wrong ... :-P

  • Use gparted to shrink any partition and gain at least 200 MB (better 500 MB) of free disk space. (If you already have a boot partition on your hard drive you can "recycle" it for this purpose instead and skip this step.)
  • Create a new partition in the free space, type "ef00" (EFI). (If you already have a boot partition on your hard drive you can "recycle" it for this purpose instead and skip this step.)
  • Format the UEFI partition with a FAT32 file system.
  • Launch gdisk, it will convert your MBR-setup into a GPT-setup. Do this at your own risk. ;-)
  • Boot a Windows 10 Setup Medium (DVD or USB pen drive).
  • Press SHIFT-F10 when the initial dialog for language-selection appears.
  • In the opening CMD enter:

    • X:\> diskpart
    • DISKPART> list disk
    • DISKPART> sel disk (your_disk_here)
    • DISKPART> list vol
    • DISKPART> sel vol (your_desired_volume_here)
    • DISKPART> assign letter=s
    • DISKPART> exit
    • X:\> bcdboot C:\Windows /s S:/f UEFI /v

  • Now reboot and switch boot order to UEFI. Done!

P. S.: Yes, there is this fabulous "MB2GPT.EXE" tool from MS which states to do the same job all in one go, even on a running OS, with only these humble restrictions (beside others):

  • There are at most 3 primary partitions in the MBR partition table.
  • The disk does not have any extended/logical partition.
  • All partitions on the disk are of MBR types recognized by Windows or has a mapping specified using the /map command-line option.

Choose your way.