How to Rebuild the BCD in Windows 10 or Windows 8.1

Rebuild Boot Configuration Data only when the startup failure points to the boot configuration. A missing disk, locked Windows volume or failing drive needs a different response. Use Startup Repair first, then identify the Windows installation and boot layout before running a command that writes boot files.

1. Prepare a recovery path

1. Record the exact error and any path it names, such as a BCD file. Note whether this started after a firmware change, disk replacement or update.
2. Back up accessible important data. Boot repair is not a backup and does not repair a physically failing disk.
3. Have compatible Windows recovery or installation media and the BitLocker recovery key, if applicable. On a work computer, contact IT before changing boot configuration.
4. Record the original firmware boot mode and boot order. Preserve an existing dual-boot or multi-disk setup with specialist help rather than applying a generic sequence.

2. Try Startup Repair

Enter Windows Recovery Environment using a working recovery route or compatible installation media's Repair your computer option. Select Troubleshoot > Advanced options > Startup Repair, supply the recovery key if requested and let it finish. Record the result.

If Windows starts, verify your files and normal restart before doing anything else. If it fails, retain the reported error or log details. Do not repeatedly cycle through the same repair without gathering new evidence.

3. Identify the installation without changing partitions

Open Troubleshoot > Advanced options > Command Prompt. These DiskPart commands list disks and volumes, then leave DiskPart; they do not select, erase or format anything:

diskpart
list disk
list volume
exit

Record disk sizes, volume labels, file systems and letters. The GPT marker is one clue about disk layout; it does not alone prove which disk the firmware boots or which Windows installation should be repaired. The Windows volume and the system/EFI partition serve different purposes. If several disks or installations make the mapping ambiguous, stop here.

For a volume you identified as a Windows candidate, check its directory. D: below is an example, not a required letter. Substitute the candidate's actual recovery-environment letter:

dir D:\Windows

A Windows folder alone does not identify the intended installation if several exist. Correlate the volume with your recorded layout and familiar files. Do not assume the usual desktop drive letters apply inside recovery.

Where available, this command reports BitLocker status without decrypting a drive:

manage-bde -status

If the required volume is locked, unlock it through the recovery workflow with the correct key before repair. If the command is unavailable or the key cannot be obtained, get assistance; do not interpret unreadable files as a missing installation.

4. Scan before rebuilding BCD

After the correct installation is accessible and the error still indicates BCD trouble, scan:

bootrec /scanos

To rebuild, run the following only after those checks. When prompted, add the installation you have positively identified; do not accept all candidates blindly:

bootrec /rebuildbcd

Record the result, restart and test. If you get an access error, a missing-device error or no useful change, stop and return to diagnosis. Do not append fixmbr, fixboot, partition deletion or BCD-renaming commands from an unrelated recipe.

5. When BCDBoot is the appropriate tool

BCDBoot recreates boot-environment files using a known Windows directory. On Windows 10, for a confirmed installation at D:\Windows and an understood system-partition/firmware layout, the basic example is:

bcdboot D:\Windows

This writes boot files and can alter boot entries or firmware boot order. It is not a read-only test. The /s option explicitly selects a system partition and changes UEFI firmware-entry behaviour; /f selects firmware type. Do not guess these values, use /f ALL as a cure-all, or format the EFI partition. For multi-boot, unusual storage or an uncertain target, have a technician choose the correct procedure and preserve the existing configuration first.

6. Verify the repair and know its limits

1. Confirm the intended Windows installation starts from its own normal boot entry, not only when recovery media is attached.
2. Check important files and applications, then perform a normal restart.
3. Confirm any other expected boot entries remain available. If encryption prompts or boot order changed unexpectedly, stop making further changes and review the recorded configuration with support.

A successful file-copy message does not prove the PC can boot. If the same failure returns, investigate storage health and the original trigger instead of repeatedly rebuilding BCD. Keep the before/after error, disk/volume notes and command results for support. Share neither recovery keys nor private file listings publicly.

There is no universal undo command for every boot layout. A BCD export alone does not capture partition contents or firmware settings. Restoring a previous configuration requires the correct backup and target; if those were not recorded, get help rather than importing another PC's BCD.

Documentation review: 7 October 2026. This is a documentation-based diagnostic workflow, not a claim of a hands-on repair. No firmware, disk partitions or boot configuration were changed for this review.

Official references