Fix Windows Error 0xc0000034 - BCD Boot Configuration Repair

You are staring at a blue screen telling you the Boot Configuration Data file is missing or corrupted with error 0xc0000034. This usually happens after a system update or an unexpected crash when the pointer to your OS files gets scrambled. We are going to rebuild the boot sector and get you back into your desktop.

Why this happens

The BCD file acts as a map for your PC, telling it exactly where your Windows files are located on your drive. When this file is corrupted or missing, your system cannot finish its startup process.

What you'll need

You will need a second working computer, a USB flash drive with at least 8GB of space, and the Windows installation media tool from the Microsoft website.

Steps

1. 01
   Create a Windows installation USB on a working PC using the official Microsoft Media Creation Tool.
2. 02
   Insert the USB into your broken PC, boot into your BIOS/UEFI settings, and move the USB to the top of your boot priority list.
3. 03
   Select your language, click 'Repair your computer', then navigate to 'Troubleshoot' > 'Advanced Options' > 'Command Prompt'.
4. 04
   Type diskpart and then list volume to identify your main Windows partition letter, then type exit to return to the prompt.
5. 05
   Run the following commands one by one: bootrec /scanos, bootrec /fixmbr, bootrec /fixboot, and bootrec /rebuildbcd.
6. 06
   If 'access is denied' appears during the fixboot command, type bootsect /nt60 sys and then run the rebuildbcd command again.
7. 07
   When asked to add the installation to the boot list, type Y. If prompted for multiple entries, only add the one pointing to your current Windows folder, not Windows.old.
8. 08
   If the rebuild fails with 'system device cannot be found', use diskpart again to select your small FAT32 partition, assign letter=B, and run bcdboot C:/windows /s B: /f UEFI (replace C with your identified drive letter).
9. 09
   Close the Command Prompt and restart your computer to boot back into Windows.

Still not working?

If you still see the error, boot back into the USB Command Prompt and run sfc /scannow followed by chkdsk C: /r to repair filesystem corruption. If zero Windows installations are found during the rebuild process, your drive's partition table may be mismatched (MBR vs GPT). In that case, you may need to convert the partition structure or perform a clean Windows install as a last resort.

Frequently asked questions

Will my files be deleted during this process?

No, these commands only repair the boot configuration files. Your personal files and installed programs remain untouched on the partition.

Why does this error keep coming back?

If this persists after a fix, it often points to a failing physical hard drive or SSD. You should back up your data immediately and check your drive's health status.