How to Rebuild the BCD in Windows 10

To rebuild the BCD (Boot Configuration Data) in Windows 10, boot into the recovery environment, open Troubleshoot > Advanced options > Command Prompt, and run bootrec /rebuildbcd. When it finds your Windows installation, type Y to add it to the boot list, then restart. On newer UEFI PCs, if that doesn’t work, recreate the boot files with bcdboot C:\Windows as shown below. Try Startup Repair first, since it fixes many boot problems automatically.

These commands fix errors like “The Boot Configuration Data file is missing,” “0xc000000f,” “BOOTMGR is missing,” and “Operating system not found.” Here’s the full process.

Step 1: Open the Windows Recovery Environment

• If Windows won’t start: Turn the PC on and off three times as the Windows logo appears. On the third try, you’ll see Preparing Automatic Repair. Click Advanced options.
• Using a USB drive: Boot from a Windows installation USB (made with the Media Creation Tool), click Next > Repair your computer.

If you’re asked for a BitLocker recovery key, see how to find your BitLocker recovery key.

Step 2: Try Startup Repair

Click Troubleshoot > Advanced options > Startup Repair and choose your Windows installation. If it succeeds, you’re done. See how to fix Startup Repair in Windows 10 if it fails.

Step 3: Rebuild the BCD with bootrec

1. Click Troubleshoot > Advanced options > Command Prompt.
2. Run these commands, pressing Enter after each:
   • bootrec /scanos
   • bootrec /rebuildbcd
3. When it lists your Windows installation and asks Add installation to boot list?, type Y and press Enter.
4. Type exit, then click Continue to restart.

Older BIOS (MBR) PCs only: you can also run bootrec /fixmbr and bootrec /fixboot. On UEFI PCs, /fixboot often says “Access is denied,” which is expected. Use Step 4 instead.

Step 4: If rebuildbcd finds 0 installations (UEFI fix)

This usually means the existing BCD needs to be recreated. On UEFI PCs, rebuild the boot files on the EFI partition:

1. In Command Prompt, type diskpart and press Enter.
2. Type list vol. Find the small (about 100 to 300 MB) FAT32 volume, labeled System. Note its number, and note which letter your Windows volume has (it may not be C: here).
3. Type sel vol 2 (replace 2 with your EFI volume number), then assign letter=S, then exit.
4. Run bcdboot C:\Windows /s S: /f UEFI, replacing C: with your Windows volume letter.
5. When you see Boot files successfully created, type exit and restart.

For legacy BIOS PCs, use bcdboot C:\Windows /s C: /f BIOS instead, or back up the store with bcdedit /export C:\bcdbackup, rename the old C:\boot\bcd file after removing its hidden attributes (attrib C:\boot\bcd -h -r -s, then ren C:\boot\bcd bcd.old), and run bootrec /rebuildbcd again.

Check your firmware settings

• Make sure the boot mode (UEFI or Legacy/CSM) matches how Windows was installed.
• Put Windows Boot Manager first in the boot order.
• Disconnect extra drives and USB devices while troubleshooting.

More help: how to fix UEFI boot in Windows 10 and how to fix “Operating system not found”.

Frequently asked questions

Will rebuilding the BCD delete my files?

No. It only changes boot configuration. Your files and apps stay put.

What does “The requested system device cannot be found” mean?

bootrec can’t find the boot partition, common on UEFI systems. Use the bcdboot method in Step 4.

What if nothing works?

Back up files from the recovery Command Prompt or by connecting the drive to another PC, then reset or reinstall Windows. A failing drive can also cause boot errors, so check its health.