Monday, August 4, 2014

How to repair UEFI Bootloader in Windows 8

In this article we will learn how to repair Windows 8 bootloader on a computer with UEFI. The corruption of the Windows 8 bootloader can occur after the installation of the second OS (in Dual Boot configurations), be caused by the erroneous actions while failure recovering and for some other reasons. If the loader in Windows 8 on UEFI system is corrupted, it’s impossible to start the system or a blue screen with the following error appears:
The boot configuration data for your PC is missing or contains errors.
File :\EFI\Microsoft\Boot\BCD
Error code: 0xc000000f
boot configuration errors 0xc000000f or missing file \EFI\Microsoft\Boot\BCD
All this can imply corruption or even total removal of Windows 8 loader configuration – Boot Configuration Data (BCD). You won’t be able to recover the BCD loader using bcdedit. When running this command, the following error appears:
The boot configuration data store could not be found.
The requested system device cannot be found
The matter is that the BCD loader configuration in Windows 8 installed in UEFI mode is stored on a separate hidden EFI volume (100 MB in size on FAT32 file system). Bcdedit can not see it and, therefore, manage the loader configuration on it.
So to recover the loader (BCD) configuration, you have to boot from the original installation Windows 8 DVD (or a recovery disk or a special EFI bootable flash drive) and open the command line choosing System Restore – > Troubleshoot-> Command Prompt or pressing Shift+F10).
system restore mode win 8
Start diskpart:
Display the list of disks in the system:
list disk
Select the disk with Windows 8 installed (if there is one disk in the system, it will have zero index):
sel disk 0
Display the list of volumes in the system:
list vol
diskpart : list volume . efi volume
In this example, you can see that the EFI volume (it can easily be recognized by its size of 100 MB and FAT32 file system) has the index volume 1, and the boot volume with Windows 8 installed isvolume 3.
Assign any disk letter to the EFI volume:
select volume 1
assign letter K:
Close diskpart:
Go to the bootloader directory in the hidden volume
cd /d k:\efi\microsoft\boot\
Recreate the boot sector on the boot partition
bootrec /fixboot
Delete the current BCD configuration file by renaming it (save the older configuration as a backup):
ren BCD BCD.bak
With bcdboot.exe, create BCD store again by copying the boot files from the system directory:
bcdboot C:\Windows /l en-us /s k: /f ALL
where C:\Windows – is the path to the directory with Windows 8 installed.
/f ALL – means that the boot files have to be copied including those for UEFI and BIOS computers (potential ability to boot in EFI and BIOS systems)
/l en-us – is a type of the system locale. By default, en-us – English (USA) is used.
Now you have to restart your computer. Then in the list of bootable devices there appears Windows Boot Manager where you can choose desired operating system to start.
About Author

Hi everyone ! I am a Fresher in Cybersec. Gaming, Learning, Sharing with the community is my hobby. I help "students" who are looking to "start" their career in Cybersecurity with my opinions that I learn from my Journey.

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