First check the hard disk connection and boot sequence in the BIOS to ensure that the system can recognize the main hard disk and the boot sequence is correct; 2. Use Windows installation media to enter repair mode, and run the bootrec /fixmbr, bootrec /fixboot, bootrec /scanos and bootrec /rebuildbcd commands in turn to repair the boot record; 3. If the automatic repair fails, you can manually rebuild the BCD. First use diskpart to confirm the partition where Windows is located, then export and rename the old BCD file, and then execute bootrec /rebuildbcd to create a new configuration; 4. Run sfc /scannow and chkdsk C: /f /r to check system file and disk errors; 5. Finally, you can try system restoration, restore from backup or reinstall Windows as the final solution. In most cases, the above steps can successfully fix the BOOTMGR missing problem.

The "BOOTMGR is missing" error in Windows usually appears when your computer can't find or load the Boot Manager, which is responsible for starting the operating system. This error prevents Windows from booting and often shows up with a prompt like "Press Ctrl Alt Del to restart." The good news is that it's usually fixed without replacing hardware. Here's how to fix it step by step.

1. Check Boot Order and Hardware Connections

Before diving into software fixes, rule out simple hardware or configuration issues:

• Restart the computer and enter the BIOS/UEFI (usually by pressing F2, F12, Delete, or Esc during startup).
• Make sure the hard drive or SSD with Windows is detected in the BIOS.
• Verify that the boot order is correct — your primary drive should be first.
• If you recently added or removed a drive, double-check that cables (especially SATA and power) are securely connected (for desktops).
• Remove any external USB drives, CDs, or other bootable media that might confuse the boot process.

If the drive isn't showing up in BIOS, it could be a sign of drive failure or connection issue.

2. Use Windows Installation Media to Repair Startup

You'll need a Windows installation USB or DVD to access the repair tools.

Steps:

• Insert the Windows installation media and boot from it (you may need to change boot order in BIOS).
• Choose your language preferences and click Next .
• Click "Repair your computer" (bottom-left corner).
• Go to Troubleshoot > Advanced Options > Command Prompt .

Now, run these commands one by one:

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

Note: If you get "Access is denied" on /fixboot , try:

 bootsect /nt60 all /force

Then run the bootrec commands again.

These commands repair the boot sector, rebuild the boot configuration data (BCD), and ensure Windows is detected.

3. Rebuild BCD Manually (If Automatic Repair Fails)

Sometimes bootrec /rebuildbcd doesn't work due to corrupted or missing BCD entries. In that case, manually recreate it:

In the Command Prompt (from installation media):

1. Identify the drive letter of your Windows installation:

    diskpart
   list volume
   exit

   Look for the volume labeled "Primary" with the Windows folder — it's often C: , but in recovery mode it might be assigned a different letter like D: or E: .

2. Assuming your Windows drive is C: , run:

    bcdedit /export C:\bcdbackup
   attrib C:\boot\bcd -h -r -s
   ren C:\boot\bcd bcd.old
   bootrec /rebuildbcd

This backs up the old BCD, removes system attributes, renames the corrupted file, and creates a new one.

4. Check for Corrupted System Files or Disk Errors

If boot files are damaged, you can attempt to repair them:

In Command Prompt (from recovery environment):

 sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows

Replace C: with your actual Windows drive letter if different.

You can also check the disk for errors:

 chkdsk C: /f /r

This may take a while, but it can fix bad sectors or file system issues.

5. Restore from System Backup or Reinstall (Last Resort)

If none of the above works:

• Try System Restore from the recovery menu if you have a restore point.
• Use a backup to restore your system.
• As a last option, reinstall Windows — this preserves the option to keep your files (but back them up first if possible).

Important Notes:

• The BOOTMGR file itself is hidden and located in the root of the system partition. Don't try to copy it manually unless you're certain of what you're doing.
• UEFI systems use a different boot process (EFI partition instead of MBR), so if you're on a newer PC, ensure you're not mixing MBR and GPT styles.

Fixing "BOOTMGR is missing" usually comes down to repairing the boot records or correcting boot configuration. Most cases can be resolved with the Windows recovery tools and a few command-line fixes.

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