Windows 10: [guide] Modifying disk UniqueId +BootLoader to point at it

Hello, im now happily re-writing my post since while intending to ask how to do it after breaking my head on it, while writing this thread it forced me to check all things and it made me realize what and how to do it, so this is now a guide.


First is the guide how to repair
Repair BCD If you've accidently changed the Disk's UniqueId and get error 0xc000000e




create a windows repair disc:
to do that download the windows media creation tool from here
https://support.microsoft.com/en-us/...f-40c3b507420d

and make a bootable usb drive, you could also download the .ISO and later use 'Rufus' application to make a bootable usb.

Insert a windows repair disc and turn on your machine, load it (you'll see the msg 'press any key to load from...'), select language, click 'Repair windows' -> click 'troubleshoot' and enter the command prompt, there you will use a tool called 'diskpart' to select your disk and then the volume with the BCD info (for me it was the one with 'Info' being set to hidden with the Fat32, I have suspicion it should've been the 'System' as Info column, but retesting it on the same drive did not work so....)
we will assign a temporary drive letter like 'T' using, and use the 'bcdboot' tool to fix the BCD
take care to note that your Disk is Gpt (when u do command list disk it will have an asterix '*' near "Gpt" tab.
if your disk is MBR (old bios) than in the last command instead of typing "/f UEFI" type "/f BIOS"
alternatively you could use '/f ALL'
commands

I'm testing this on a virtual machine but it should not matter at all.
on my machine there is only 1 disk labeled 'C', in the 'set disk' command you will have to select the correct number if you have more than one disk.

Code:

and that's it, windows should boot, on a side note you can go ahead and delete the old boot config so windows will not ask you from where you want to boot windows.
open 'System configuration' (run -> msconfig)
go to 'Boot' tab and delete the boot that is NOT the 'Current OS; Default OS'









HOW TO CHANGE
bootable Disk's UniqueId and Set the BCD to load from it

Generate a new UID:
open powershell.exe as an admin and type
[guid]::NewGuid().ToString()

this will print out a newly created uid for you, select and copy it
for example I got this
bef16cfc-76a1-440a-9c4b-673d5eb59634

Now type the command 'diskpart'

diskpart
sel disk 0
UniqueId disk id=bef16cfc-76a1-440a-9c4b-673d5eb59634
replace the Id with your own UniqueId

The problem as you know is that changing the UniqueId in diskpart will not notify and update the BCD/bootloader itself of the change thus rebooting the system will result in a 0xc000000e error and renders everything useless as windows would not be able to boot or even enter repair mode (without the repair disc)


Update BCD

We are going to correctly identify where your current Windows Boot Manager resides
for that we will first label all volumes on the disk (this is temporary dont worry)
in diskpart we will list all the volumes in the current disk
Diskpart
list disk
select disk 0 (or your other disk?)
list vol

instead of 'NUMBER' type the number of the volume that does not have a Ltr (letter)
most likely you will have 2 volumes that do not have letters, give each volume a different unused label lets say T: and W:
select vol NUMBER
assign letter=T:
^ repeat this for all volumes with no Ltr (change T: to a different letter each time likw W, X, Y...)

now open CMD with admin privileges (or use powershell, although I've had some issues with that with bcdedit /store...)
type
bcdedit /enum /v
It will show you a list with the first entry being "Windows Boot Manager"
and the rest will be a few "Windows Boot Loader" entries
look at the Device and Path of the boot manager, for me it's partition=T:\EFI\Microsoft\Boot\bootmgfw.efi
so now we know it's in volume
T:

now we will edit the "Windows Boot Loader"
most likely your second entry (the first "windows boot loader")
is the boot loader that you want to update
you will see that the "device" and "osdevice" are 'unkown'



(*edit in this image u dont see my boot manager device letter because I took the screenshot before assigning one, but it was drive letter 'T')
copy the "Identitfier" guid of the Boot Loader
we will change the 'device' and 'osdevice' to point to our C partition

bcdedit /store T:\EFI\Microsoft\Boot\BCD /set {LOADER_IDENTIFIER_WE_COPIED} device partition=C:
bcdedit /store T:\EFI\Microsoft\Boot\BCD /set {LOADER_IDENTIFIER_WE_COPIED} osdevice partition=C:

replace T:\EFI\..... with the drive letter that we got from the 'boot manager' earlier
and that's it, we're good
you can later delete the previous bootloader using System info (msconfig) I showed how earlier in this tut




Incase you can't detect the bcd drive letter and it says 'Uknown' on the "Window boot manager" device, it means it did not detect a BCD at all, look up google on how to try to locate your bcd and if it still doesnt find it you'll have to create a fresh new BCD
reference this microsoft doc page and look for guides on creating new bcd
https://docs.microsoft.com/en-us/win...d-line-options

:)

 

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Disk offline because it has signature collision with another disk online

Based on your suggestion such as "You may clean old disk to remove all information from it and reinitialize it. Run diskpart utility and use clean command. Be careful to not clean new disk.

Change identifier using uniqueid command of diskpart. "

what will be the next step?

 

How to make Windows 10 bootloader As default bootloader

If you're using UEFI, you might have to use that to edit.
Modified from here:
How to set Windows bootloader as default bootloader?

To repair your Windows bootloader, if you have a Windows CD

1. Boot from CD
   
2. From title screen, open terminal (the button is usually in bottom left corner)
   
3. Execute bootrec /fixmbr
   
   If this doesn't give desired results, try bootrec /fixboot