Fix "BOOTMGR is missing" on Windows 10/11 (Exact Commands)

The fast answer. "BOOTMGR is missing — Press Ctrl+Alt+Del to restart" means the BIOS found a disk but couldn’t find the Windows Boot Manager (bootmgr) on it. The most common cause is booting from the wrong device — unplug every USB drive and external disk and reboot first. If it persists, the boot sector or the active-partition flag is damaged. Boot into Windows Recovery (WinRE) and run:

bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

Then reboot. If that fails, the System Reserved partition may not be marked active — fix it with diskpart (Step 5 below).

Why this happens

Booting from wrong device — a non-bootable USB, external disk, or CD/DVD is ahead of the real boot drive in the BIOS boot order. Most common cause and the easiest to fix.
Wrong partition set active — on MBR disks, the System Reserved (or boot) partition must be marked active. A disk clone, partition resize, or accidental diskpart command can clear that flag.
Damaged boot sector or MBR — an unclean shutdown, malware, or power failure corrupted the master boot record or the partition’s boot sector where bootmgr is loaded from.
Corrupted or missing BCD store — the Boot Configuration Data file (\Boot\BCD) is damaged or deleted, so the boot manager can’t find Windows.
Loose or failing drive — a SATA cable, M.2 connection, or the drive itself intermittently drops, making the boot volume unreadable.

Step-by-step fix

Step 1 — Remove external media and check boot order

Unplug every USB drive, external disk, and SD card. Remove any CD/DVD. Then reboot. If the machine starts normally, the BIOS was simply booting from the wrong device. To prevent a repeat, enter BIOS/UEFI setup (usually Del, F2, or Esc at power-on) and move your internal drive to the top of the boot order.

Step 2 — Get into Windows Recovery (WinRE)

Force three failed boots (power on, then hold the power button to kill it as the Windows logo appears, three times) and Windows opens Automatic Repair. Or boot from a Windows 10/11 install USB and choose Repair your computer. Then go to Troubleshoot → Advanced options.

Step 3 — Run Startup Repair

In Advanced options, choose Startup Repair. This automated tool detects and fixes missing or corrupted boot files — including a missing bootmgr — without any manual commands. Let it finish and reboot. If Startup Repair reports it couldn’t fix the problem, continue to Step 4.

Step 4 — Rebuild the boot configuration

In Advanced options → Command Prompt, run these in order:

bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

/fixmbr writes a fresh master boot record. /fixboot writes a new boot sector on the active partition. /rebuildbcd scans for Windows installations — when it finds one, type Y to add it. Reboot and test.

UEFI/GPT note: on modern UEFI systems bootrec /fixboot can return "Access is denied". That’s expected — UEFI has no legacy boot sector to fix. Skip to Step 6 and use bcdboot instead. See the bcdboot procedure for the full walkthrough.

Step 5 — Set the correct partition active (MBR/legacy BIOS)

If the boot configuration looks fine but bootmgr still isn’t found, the wrong partition may be active. In WinRE Command Prompt:

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

Replace sel partition 1 with the actual System Reserved or boot partition — it’s typically a small (100–500 MB) NTFS partition. Setting the wrong partition active makes things worse, so confirm the number before you type active. Reboot and test.

Note: the active command applies only to MBR disks. UEFI/GPT systems use the EFI System Partition and do not need an active flag — use bcdboot in Step 6 instead.

Step 6 — Rebuild boot files with bcdboot

If the steps above didn’t work — or you’re on a UEFI/GPT system — rebuild the boot files directly. In WinRE Command Prompt, confirm your Windows drive letter (it may not be C: inside WinRE) and run:

bcdboot C:\Windows

On UEFI/GPT, assign a letter to the EFI System Partition first and specify it:

diskpart
list vol
sel vol <EFI-FAT32-vol#>
assign letter=S:
exit
bcdboot C:\Windows /s S: /f UEFI

You should see "Boot files successfully created." Reboot and test.

Step 7 — Check disk health

If the error keeps returning, the drive may have bad sectors affecting the boot area. From WinRE Command Prompt:

chkdsk C: /f /r

Replace C: with the Windows drive letter shown in WinRE. If chkdsk reports a large number of bad sectors, the drive is failing — back up immediately and replace it.

Data safety: bootrec, diskpart active, and bcdboot only touch boot metadata, not your files. chkdsk /f /r is safe on a healthy drive but stresses weak sectors on a failing one. If this machine holds the only copy of data you can’t lose, image the drive to a known-good external disk before running chkdsk. Never run format or clean in diskpart — those destroy data.

GRAM tip: The repair steps above run in Windows Recovery, which is already on the broken PC. Once the machine boots again, plug in GRAM — a free portable repair toolkit that runs from a USB inside Windows — to check the disk’s SMART health and event logs, read the boot configuration, and let its AI agent confirm the root cause so the error doesn’t come back.

Download GRAM free See AI pricing →

FAQ

Can I fix this without a second working computer?

Yes. Windows Recovery (WinRE) lives on the broken PC itself — force three failed boots to trigger Automatic Repair, or boot from any Windows install USB. All the commands above run inside WinRE. No second computer is required. (GRAM runs inside Windows rather than from boot media — use it once the machine boots to verify disk health and confirm the root cause.)

Is "BOOTMGR is missing" the same error on UEFI and legacy BIOS?

BOOTMGR is the legacy BIOS boot manager file. On a pure UEFI/GPT system, the equivalent is bootmgfw.efi in the EFI System Partition, and a missing bootloader typically shows error 0xc000000e instead. You’ll see "BOOTMGR is missing" on legacy BIOS machines, or UEFI machines running in CSM (Compatibility Support Module) mode. Either way, bcdboot (Step 6) rebuilds the correct boot files for your firmware type.

Will setting a partition active erase my data?

No. The active flag in diskpart is a single bit in the partition table — it tells the BIOS which partition to boot from. It does not format, overwrite, or delete anything on the partition. The risk is setting the wrong partition active, which can change the error rather than fix it. If that happens, re-run diskpart and mark the correct partition.

Could a disk clone or partition resize cause this?

Yes. If a clone tool copies the data but doesn’t mark the System Reserved partition as active, or if a partition resize moved the boot files without updating the MBR, the BIOS will fail to find bootmgr. Fix it by setting the correct partition active (Step 5) and rebuilding the boot configuration (Step 4 or Step 6).