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Add missing EFI partition

Note

This article assumes you are using a UEFI system with a GPT hard drive.

The error

There is no boot entry for windows. The hard drive is not bootable.

The reason

The EFI system Partition is missing.

The solution

  1. Use a Windows installation media to gain access to a command prompt.

  2. Run diskpart to create an EFI System partition.

    C:\Windows>diskpart

  3. Select the disk and partition that windows is installed on

    DISKPART> list disk
DISKPART> select disk <n> -- (1)!
DISKPART> list partition
DISKPART> select partition <n> -- (2)!
    1. Change <n> to the desired disk number
    2. Change <n> to the desired partition number

  4. Add the EFI system partition

    DISKPART> shrink desired=500
DISKPART> create partition efi
DISKPART> format fs=fat32 quick
DISKPART> assign letter=Y
DISKPART> exit

  5. Add the boot files to the ESP using bcdboot.

    C:\Windows>bcdboot C:\Windows /s Y: -- (1)!
    1. /s specifies the volume letter.

Further reading