Can you open Elevated Command Prompt from Command Prompt?

I think the user needs to get a list of working disks and their associated drive letters while booted into the WinPE environment. I believe launching a command prompt, running diskpart, then typing "list volume" will do the trick. Here's what that produces in Powershell on my production PC, for example:

Then, the OP can use the drive letter for the drive in need of attention going forward after that.
HTH,
--Ed--

PS: I just did this on a laptop booted to WinPE and it showed my usual C: drive as E:, for example. Expect assignments to move around when another Windows image is in charge!

This means that bcdedit finds no boot configuration data on the d: drive (which I'm guessing is your normal boot/sys drive). When I run that on my WinPE-booted laptop it does indeed show that Windows Boot Manager, and the default boot loader, both reside on my E: (your D ) drive.

Something is definitely not right! This means the BCD needs to be rebuilt. You can try the suggestions earlier in this thread (or on the forums elsewhere: see thread #241 at Create Windows 10 ISO image from Existing Installation - Page 25 - help Installation Upgrade Tutorials , where you'll find this item:

If you getting "An operting system wasn't found."
1- Boot with installation media or whatever.
2- Shift + f10 (command promt)
3- bootrec /rebuildbcd
4- bootrec /fixmbr
5- bootrec /fixboot
6- reboot your system. If you cant still boot, boot with installation media again and use Windows Repair.

Windows repair doesnt work if you dont "rebuilBcd".

Lines 3-5 are the key instructions here.
HTH,
--Ed--

Looks like the drive is hosed. If you don't have a backup and you need the drive's contents, it's now time for data recovery. If you do have a backup and/or you don't care about the drive's contents, you could format the drive (or go into diskmgmt.msc and add it as a volume). But that drive's contents are not readily accessible anymore. At a minimum your MBR or GPT data has been corrupted or destroyed. You could try repairing same using the free MiniTool Partition Wizard to see if recovering the partition data will fix it. If not, something more serious and expensive will be needed.

PS/Warning!: DO NOT WRITE ANYTHING to this drive until you decide if you're going to try to recover its contents or not. Anything you write to it now is only going to further complicate recovery efforts, and may end up over-writing and destroying stuff you might instead want to recover and copy onto another drive.

HTH,
--Ed--

The first command tells you that bootrec is finding zero, or none, windows installations. It can't see the OS files, nor find them, apparently. Fixmbr can't work unless there's something to fix. As I said in my previous message, your partition data is corrupted or destroyed. Until you fix that (or start over) none of the boot repair operations can do anything at all. Sorry for your troubles!
--Ed--