WinPE: Boot in UEFI or legacy BIOS mode
When you boot Windows PE on a UEFI PC, you may need to check whether the PC is booted in UEFI mode or legacy BIOS-compatibility mode.
For example, running Windows Setup through Windows PE requires you to be in the correct firmware mode.
For many operations, such as applying Windows images using Diskpart and DISM, the firmware mode might not make a difference.
For more in-depth details on booting to UEFI or BIOS mode, see Boot to UEFI mode or legacy BIOS mode.
Boot to UEFI mode
When booting the PC, you may need to manually select the UEFI boot files: \EFI\BOOT\BOOTX64.EFI.
Boot your PC and press the key to get into the firmware menus (examples: Esc, F2, F9, F12).
Look for a firmware option to choose the boot file (examples: Boot to file, Boot to EFI file).
Select the file from the USB drive:
Detect whether Windows PE is booted in BIOS or UEFI mode
Once you're booted into WinPE, you can check to see which mode you've booted into. If you want to know which mode WinPE is in every time you boot, you can add a script that checks to your WinPE image. See Wpeinit and Startnet.cmd: Using WinPE startup scripts for more information.
Check the HKLM\System\CurrentControlSet\Control\PEFirmwareType registry value to see if the PC is booted to UEFI or BIOS mode. Note: you may need to run
wpeutil UpdateBootInfoto make sure this value is present.
reg query HKLM\System\CurrentControlSet\Control /v PEFirmwareType
This command returns 0x1 if the PC is booted into BIOS mode, or 0x2 if the PC is booted in UEFI mode.
wpeutil UpdateBootInfo for /f "tokens=2* delims= " %%A in ('reg query HKLM\System\CurrentControlSet\Control /v PEFirmwareType') DO SET Firmware=%%B :: Note: delims is a TAB followed by a space. if %Firmware%==0x1 echo The PC is booted in BIOS mode. if %Firmware%==0x2 echo The PC is booted in UEFI mode.
If this is a frequent problem, you can remove the boot files for UEFI mode or BIOS mode to prevent the PC from booting in the wrong mode. If the PC firmware is set up to boot in the wrong mode, the media will immediately fail to boot, allowing you to immediately retry booting the PC into the correct mode.
Boot in UEFI mode: To prevent Windows PE from booting in BIOS mode, remove the bootmgr file on the root of the media.
Boot in BIOS mode: To prevent Windows PE from booting in UEFI mode, remove the efi folder on the root of the media.