Problems booting Windows – converting MBR to GPT to UEFI Secure Boot

admin

Hi!

This is the reason why your bcdboot failed.

You tried manually creating the EFI partition (150 MB FAT32) — good idea, but:

  • If the disk is still MBR, UEFI firmware won’t recognize it, even with an EFI partition.

bcdboot needs a GPT disk with a properly flagged EFI partition (EFI System Partition type).

  • On MBR, your EFI partition is just another FAT32 volume, so it fails with [c000000f].
  • If you really want to reuse the one you made: a. Convert the disk to GPT (use mbr2gpt /convert, it won’t erase data). b. Make sure your 150MB partition is marked as EFI System Partition (ESP):
  • diskpart

list disk

sel disk 0

list part

sel part X

set id=c12a7328-f81f-11d2-ba4b-00a0c93ec93b

gpt attributes=0x8000000000000001

exit

c. Then run:

  • bcdboot C:\Windows /s G: /f UEFI

That will copy the boot files to your EFI.

My suggestion is to use a built-in tool called MBR2GPT, which is designed for exactly this purpose. It creates the EFI partition, converts the disk, and writes the UEFI boot files automatically. (Let me know if you want this approach)

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