Windows won’t start

'BOOTMGR is missing' error on startup

Windows displays 'BOOTMGR is missing, press Ctrl+Alt+Del to restart' instead of loading. The Windows Boot Manager file it needs has been deleted, corrupted, or can't be found on the drive.

Difficulty
Intermediate
Time
20–60 minutes
DIY cost
$0
Pro cost
$100–$200

Symptoms

  • Black screen with BOOTMGR is missing text
  • Restarting with Ctrl+Alt+Delete just repeats the message
  • May follow a failed update, virus removal, or a new drive being added
  • Windows was working normally before this appeared

Likely causes

  • CommonBoot files corrupted or deletedMalware removal tools or improper shutdowns can damage these small critical files.
  • CommonBoot order in BIOS pointing to the wrong driveAdding a second drive or USB device can shift which disk the PC tries first.
  • PossibleFailing hard drive with bad sectors in the boot areaPhysical drive damage can wipe out just the boot files while the rest of the data survives.
  • PossibleImproperly cloned or partitioned driveA botched drive clone or resize can leave boot files inconsistent.
  • Less commonIncompatible or loose secondary driveA second drive with its own boot sector can confuse the BIOS.

What to do

  1. Remove any USB drives or discs and restart to rule out the PC trying to boot from the wrong media.
  2. Enter BIOS/UEFI and verify the correct internal drive is set as the first boot device.
  3. Boot from a Windows installation USB, choose 'Repair your computer,' then open Command Prompt.
  4. Run 'bootrec /fixmbr', then 'bootrec /fixboot', then 'bootrec /rebuildbcd' in order, restarting between attempts if needed.
  5. If rebuildbcd finds no Windows installations, try 'bootrec /scanos' first to locate them.
  6. If the drive has bad sectors, run 'chkdsk C: /r' from the same recovery Command Prompt.
  7. If none of the bootrec commands succeed, the boot sector or drive itself may need a fresh format and reinstall, so back up data first if the drive is still readable.

Tools and parts

  • Bootable Windows installation USB drive

When to call a pro

If bootrec commands fail repeatedly or chkdsk reports serious errors, a professional can attempt data recovery before reformatting the drive.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.