Repair Windows 8 EFI Bootloader

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Repair Windows 8 EFI Bootloader

December 5, 2015 | Article | 2 Comments

Suppose you have installed Windows 8 on your machine. After an unexpected incidents you can not boot your Windows anymore, what will you do? Reinstall? No, let’s fix it!
This article will discuss about how to repair / fix Windows 8 Bootloader. For simplification, we have following assumption:

  1. Our machine is EFI-based with GPT disk (thus have EFI partition on first partition)
  2. You have Windows 8 installer (yes, we use installer DVD to do)

Now boot into your machine wit Windows 8 installer. Do normal method until you are prompted with list of volumes / partitions. Now press [Shift] + F10. This will bring you alovely black-themed cmd ๐Ÿ˜€

Now invoke following commands:

diskpart

Then you will be brought to a diskpart program. First we must now what your disk (the one windows 8 installed). To do so we will issue this command:

list disk

Now you will see a list of disk you have numbered by a value from 0. In this article I assume we have 1 disk and the installed windows on disk 0. If not, change 0 with appropriate number. Now execute this:

sel disk 0

Now list the volumes by invoking:

list vol

At minimal you have 1 EFI partition, 1 MSR partition, and 1 primary partition. Look at the output and write down the letter the partition use. In this article I assume the windows partition has letter C:ย  as shown below. The red square means the volume / partition of my EFI partition and blue one means the partition where my Windows installed.

diskpart

To change a volume letter (i.e: from b: to c:, etc) follow this commands:

sel vol #
assign letter n:

Where # is the volume you want to assign with and n is a drive letter (b,c,d, etc).

Now assign EFI partition to B: (in this article I have vol 1):

sel vol 1
assign letter b:

On successful attempt you will be prompted that the volume has been assign to letter b.Then exit diskpart with exit command. Now go to the EFI partition and fix the boot:

cd /d b:\EFI\Microsoft\Boot\
bootrec /fixboot

Now delete (or rename) the BCD file:

ren BCD BCD.bak

Then use bcdboot.exe to recreate BCD store.

bcdboot C:\Windows /l en-us /s B: /f ALL

Where C:\Windows is our installed windows on drive C: and B: is drive of our EFI partition. The /f ALL parameter updates the BIOS settings including UEFI firmware/NVRAM, while /l en-us is to localise for US locale, it will default to US English.

To re-enable Hyper-V, we should run the following commands:

bcdedit /set {default} hypervisorlaunchtype Auto
bcdedit /set {default} nx OptIn

Now reboot and wish you luck ๐Ÿ˜€

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About Author

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xathrya

A man who is obsessed to low level technology.

2 Comments
  1. Deploying Windows Server 2012 without Running Installer - Xathrya.ID

    […] entry in UEFI firmware isn’t match with those modified layout. So I change back to GPT and repair the UEFI bootloader for Windows 8, while the Slackware remain untouched […]

  2. Creating Dual Boot System with Windows 8 and Slackware64 on UEFI-based Machine - Xathrya.ID

    […] Now, to create a bootstrap we first need to restart the machine and boot with Windows 8 installation DVD. What we will do is repair the Windows 8 EFI bootloader. […]

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