Introduction

If your Windows machine fails to boot with errors like:

• 0xc0000098

• “A required device isn’t connected or can’t be accessed.”

• “No bootable device.”

• Missing or corrupt, BCD or bootmgfw.efi

…it’s likely your UEFI boot configuration is broken.

This guide shows how to repair Windows UEFI boot without reinstalling the OS or losing data — using only built-in tools from the Windows installation media.

Step 1: Boot from Windows Installation ISO

1. Boot the system using a Windows installation ISO (USB, DVD, or virtual ISO)
2. Next, click “Repair your computer” in the bottom-left corner. Navigate to:
   Troubleshoot → Advanced options → Command Prompt
   — or simply press Shift + F10 to open it directly.

   

   

Step 2: Run These Commands (In Exact Order)

These steps repair the bootloader and rebuild the UEFI boot configuration.

1. Scan and repair boot structures

2. Assign drive letters to the Windows and EFI partitions

select volume 1 :: Usually the Windows OS partition 
assign letter=C 
select volume 2 :: Usually the EFI System Partition (FAT32)
assign letter=E
exit

Ensure:

• C: points to your Windows installation (C:\Windows)

• E: Is your EFI partition (small, ~100–300MB, FAT32)

3. Rebuild the EFI boot files

This command copies boot files to the EFI partition and creates a fresh BCD store.

4. Optional: View current boot configuration

Useful for verifying that the system now has correct boot entries.

Step 3: Reboot

Before rebooting:

• Detach the ISO or USB if needed

Then:

The system should now boot into Windows normally.

Conclusion

By following these steps, you’ve:

• Repaired a corrupted or missing UEFI bootloader

• Rebuilt the BCD store from your existing OS

• Avoided full reinstallation and preserved your data

This is a reliable and repeatable method for resolving common UEFI boot failures on Windows systems.