What does 'BOOTMGR is missing' mean?

The short answer

Your computer can’t find the Windows Boot Manager, a small but essential file it needs to start Windows, so it gets stuck and refuses to boot.

Why does it happen?

BOOTMGR (Boot Manager) is a tiny file that lives on your hard drive and tells your computer how to load Windows. When it’s missing or damaged, your PC has no idea how to start. Common causes include:

  • A corrupted or deleted boot file — a bad shutdown, power outage, or malware damaged the Boot Manager file
  • Wrong boot order — your computer is trying to start from a USB drive, CD, or external drive that doesn’t have an operating system
  • A failing hard drive — the drive where BOOTMGR lives is starting to die or has bad sectors
  • A botched Windows update or install — something went wrong during an update and the boot files got overwritten or removed
  • Loose drive cables — the physical connection to your hard drive came undone

How to fix it

Try these steps in order:

  1. Remove all USB drives and discs — unplug any USB sticks, external drives, or DVDs and restart your computer
  2. Check the boot order in BIOS — press F2, F12, or Delete during startup and make sure your main hard drive is listed first
  3. Run Startup Repair — boot from a Windows installation USB, select “Repair your computer,” then choose “Startup Repair”
  4. Rebuild boot files manually — from the Windows recovery command prompt, run bootrec /fixboot and bootrec /rebuildbcd
  5. Check your hard drive — use your PC manufacturer’s built-in diagnostics (usually in BIOS) to test if the drive is healthy
  6. Reinstall Windows — if nothing else works, you may need a fresh Windows installation (back up your data first if possible)

When should you worry?

If removing a USB drive or fixing the boot order solves it, there’s nothing to worry about. But if the error keeps appearing:

  • Your hard drive may be failing — back up your files immediately and plan to replace the drive
  • Your Windows installation may be beyond repair — a clean reinstall is sometimes the only option
  • Repeated power outages can cause this — consider using a surge protector or UPS to prevent future boot file corruption

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