NEED HELP: How to repair an UEFI bootable windows 10 disk

So all I should need to do is assign a letter, label it, change the type and then run startip repair?

It is easy to add an EFI System Partition and set it up for booting, but I'm riding in a car on my phone for a couple hours.

Assuming that you are booted into something that will give you a command prompt with administrator rights, such as Kyhi's Recovery Tools or a Windows 10 installation drive, here's how to add an EFI System Partition to the drive that doesn't have one (it has to be connected to the computer, obviously). This is assuming that you have already set the Windows 10 partition to the correct ID type using the previously provided commands.

diskpart
list disk
select disk # <- replace # with the disk number you need to work on
list part
select part # <- replace # with the partition containing the Windows files (C:\Windows)
shrink desired=100
create part efi
format fs=fat32 quick
assign letter=z
exit
bcdboot C:\Windows /s z: /f UEFI
exit

That should do it. Now, whatever you are booted into may not assign the Windows partition the letter C:. It might assign it some other letter like D: or E: or whatever. If that is the case, just change the drive letter in red in the bcdboot command to whatever is assigned to the Windows partition. Don't worry, when you actually boot into it, it will get C: drive.

Now I have my old main SSD up and running as it was again and currently taking a backup of it as is.

Just want to thank you both again for taking your time with me over these last two days.
I appreciate it a lot, so thank you. You guys are life saviors without risking your own life.

You're most welcome. Glad it worked for you!

dalchina said:

Is that also UEFI - you mentioned one was MBR?

Note: make sure that having been inducted into disk imaging, you now use it routinely to maintain periodically updated image sets for every disk you have. Macrium's option Backup, Windows Backup, will select all partitions needed for Windows.

Once you have those, you've a good chance of recovering easily from ransomware, disk failure, user error, cosmic rays, alien invasion.... (well, not the last, but you get the idea) - and having a second chance- relatively quickly, without technical help.

You forgot, massive EMP/CME. But I'm sure you have your backup PC in a secure Faraday cage, right?