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Windows Boot Problems

On UEFI systems the firmware loads the Windows Boot Manager (\EFI\Microsoft\Boot\bootmgfw.efi) from the small EFI system partition (ESP). It reads the boot configuration (BCD) next to it and starts Windows from the C: partition. If the ESP or BCD is damaged, Windows itself is usually fine and only the boot files need to be recreated.

flowchart LR
  uefi[UEFI] --> esp["EFI partition<br/>Boot Manager + BCD"]
  esp --> winload["C:<br/>winload.efi"]
  winload --> windows[Windows]

Repairing the bootloader

Section titled “Repairing the bootloader”

  1. Boot from a Windows installation USB drive.

  2. Press Shift+F10 on the first setup screen to open a command prompt.

  3. Find the partitions and give the ESP a drive letter:

    Terminal window
    diskpart
    list volume
    select volume 3
    assign letter=S
    exit

    The ESP is the small (100–500 MB) FAT32 volume, often labelled System. Also note the letter of the Windows volume: in the installer it is not always C:.

  4. Recreate the boot files and BCD, with the Windows volume as the source:

    Terminal window
    bcdboot C:\Windows /s S: /f UEFI

  5. Restart without the USB drive.

The temporary letter S: disappears on restart, so remove letter=S in diskpart is optional.