Will rebuilding the BCD delete my files?

No. It only writes to the small boot partition. Your data on C: is untouched.

Why did BOOTMGR disappear in the first place?

Usually a sudden power loss, a failed Windows update, or accidentally formatting the wrong partition.

⏻ Boot & Startup Errors

BOOTMGR is missing — How to fix on Windows 11/10

BOOTMGR is missing means Windows cannot find the boot manager file at startup. The file is almost always recoverable — you just need the Windows Recovery Environment.

Time: 25 min
Difficulty: medium
Applies to: Windows 11, Windows 10
Updated: May 25, 2026

Error message

BOOTMGR is missing. Press Ctrl + Alt + Del to restart.

Symptoms

▸Black screen with "BOOTMGR is missing" message
▸PC reboots to the same error after pressing Ctrl + Alt + Del
▸BIOS shows the boot drive but Windows never loads

Likely causes

▸BCD (Boot Configuration Data) store is corrupted
▸Boot partition damaged after a power loss
▸Wrong boot device priority in BIOS
▸Damaged MBR / GPT partition table

How to fix it — step by step

01
Check BIOS boot order
Enter BIOS (usually F2 / Del). Make sure the Windows boot drive is first in the boot order. Disable any USB or network boot options taking priority.
02
Boot from Windows installation media
Use a Windows 10/11 installer USB (created with the Media Creation Tool). Boot from it, click Next → Repair your computer → Troubleshoot → Advanced options → Command Prompt.

Rebuild the BCD

Run each command in order:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

Mark the system partition active (MBR disks only)

Inside Command Prompt:

diskpart
list disk
select disk 0
list partition
select partition 1
active
exit

05
If on UEFI/GPT, repair the EFI partition
Identify the EFI partition (FAT32, ~100 MB), assign a letter, and rebuild boot files there.
```
diskpart
select disk 0
list partition
select partition 1
assign letter=Z
exit
bcdboot C:\Windows /s Z: /f UEFI
```