Fixing the blue screen "0xc000000e A required device isn't connected or can't be accessed"

My parents' Windows 10 PC was showing a blue screen on startup:

Your PC needs to be repaired. A required device isn't connected or can't be accessed. Error code: 0xc000000e

When pressing F8, the screen would blink and show a slightly different message that said that \Windows\system32\winload.exe was missing.

In multiple places on the Internet, people were indicating that it might have something to do with the "BCD".

I had two SATA SSD disks:

• Disk 0 was the old disk that I was booting from a while back. This disk had become un-bootable a few months ago due to a failed attempt of cloning the contents of "disk 1" into "disk 0".
• Disk 1 is the disk with the current installation of Windows. Originally, this disk was in a machine that only supported BIOS boot (no EFI).

In the Stackoverflow page Unable to boot Windows 10 after cloning to SSD, a user suggested to boot from a USB disk with a Windows installation ISO, which I did. I select "Repair my computer", and pressed Maj+F10 to spaw a command prompt. I listed the volumes:

diskpart
> list vol

I tried the following:

bootrec /rebuildbcd

It would end with the error message "multiple indistinguishable devices":

Total identified Windows installations: 1
[1] F:\Windows
Add installation to boot list? Yes(Y)/No(N)/All(A):y

The requested system device cannot be identified due to multiple indistinguishable devices potentially matching the identification 
criteria.

I tried two other commands. "fixboot" was failing with "access refused".

$ bootrec /fixmbr
The operation completed successfully.

$ bootrec /fixboot
Access is denied.

Also, bcdboot would not work:

$ bcdboot F:\Windows
Failure when attempting to copy boot files.

I think that's because the Boot folder isn't in my system partition F:\. Instead, it is in my system protected partition I:\:

$ dir /a I:\

I also realized that this disk was using an MBR (master boot record), which meant I would not be able to use the EFI boot method since it requires a GPT disk. So I tried mbr2gpt:

$ mbr2gpt /validate /disk:1
Cannot find Os partition(s) for disk 1

In the post https://www.diskpart.com/gpt-mbr/mbr2gpt-cannot-find-os-partition-7201.html, it is suggested to check the contents of the BCD file. But the command fails for me:

$ bcdedit /enum all
The boot configuration data store could not be opened.
The system cannot find the file specified.

The person also suggest giving the command the path to the BCD file. This time, it works:

bcdedit /store I:\boot\bcd /enum all

As you can see, the device and osdevice both say unknown for {bootmgr} and {default}.

At this point, I fixed up the entries {bootmgr} and {default}:

bcdedit /store I:\boot\bcd /set {bootmgr} device partition=F:
bcdedit /store I:\boot\bcd /set {default} device partition=F:
bcdedit /store I:\boot\bcd /set {default} osdevice partition=F:

and I deleted the entries that I wasn't able to fix like the "Recovery" one and most of the others:

bcdedit /store I:\boot\bcd /delete {65dd1b0e-acc2-11eb-bee2-de199bbf30c3}

NOTE: don't worry about messing the BCD, you can bootrec /rebuildbcd to fix everything. Actually, I should have moved from MBR to GPT after fixing bootrec /rebuildbcd.

Then, mbr2gpt started working:

$ mbr2gpt /convert /disk:1
MBR2GPT will now attempt to convert the default book disk.
If conversion is successful the disk can only be booted in GPT mode.
These changes cannot be undone!

MBR2GPT: Attempting to convert disk 0
MBR2GPT: Retrieving layout of disk
MBR2GPT: Validating layout, disk sector size is: 512 bytes
MBR2GPT: Trying to shrink the system partition
MBR2GPT: Trying to shrink the OS partition
MBR2GPT: Creating the EFI system partition
MBR2GPT: Installing the new boot files
MBR2GPT: Performing the layout conversion
MBR2GPT: Migrating default boot entry
MBR2GPT: Adding recovery boot entry
MBR2GPT: Fixing drive letter mapping
MBR2GPT: Conversion completed successfully
MBR2GPT: Before the new system can boot properly you need to switch the firmware to boot to UEFI mode!

Back to the problem with bootrec /rebuildbcd. was the only way to move forward, since my BCD file seemed to be completely off. The "multiple indistinguishable devices" had to be the key of the problem.

One thing that was suggested on Reddit to fix "multiple indistinguishable devices" was to "recreate" the system protected partition. It is actually very easy:

diskpart
set disk 1
set part 1
assign letter i

# Make sure that this partition isn't
# the partition that has \Windows in it.
# It should have \Boot and \bootmgr at
# its root.

format quick fs=fat32 label=System

Then, re-copy the boot files to it:

bcdboot F:\Windows /s I: /f ALL

You should now see the Boot folder:

In https://www.bleepingcomputer.com/forums/t/709202/windows-wont-boot-properly-resulting-in-error-code-0x0000007b/page-2, a user also reported "multiple indistinguishable devices". He mentioned something about multiple partitions that had the type "System protected partition". He mentioned the last 5 characters of the partition ID:

Partition Type	Partition ID
EFI	c12a7328-f81f-11d2-ba4b-00a0c93ec93b
Data	ebd0a0a2-b9e5-4433-87c0-68b6b72699c7

I realized that I had two "EFI" partitions: the one on disk 1 (expected), and the one on the USB disk:

So I changed the ID on the USB partition and it started working!

diskpart
set disk 2
set part 1
set id=c12a7328-f81f-11d2-ba4b-00a0c93ec93699c7

And then:

bootrec /rebuildbcd

and it worked! The machine finally started booting to Windows 10.