sfc /scannow WILL NOT function

(1) Yeah, sounds like SFC is not the solution. DISM & SFC do often disappoint. Even when they do run successfully (even "fixing" something), the problem they were run for doesn't go away. That sounds like a sin, but I guess it means the problem is something other than a bad system file. But does it work in Windows too now? We want it to work there.

(2) That clarification makes me think the Built-In Administrator is turned ON. What is the reason for that? Careful, though, don't turn it off unless there is at least one other Administrator account. That would be a bundle of trouble fixed only with a clean install or a system image restore. Is that the password you have forgotten, the one for the Built-In Administrator?

(3) "A lot of type came up which I thought you'd like to see"

You can copy text at any Command Prompt by selecting it with the mouse (or use Ctrl-A to select all of it), then press Ctrl-C. After that, type "Notepad" at the Command Prompt, & paste it (Ctrl-V) into a text file. The file will be there after you boot back to Windows. Practice it while booted to Windows to see what you've got to click & type into the name box. Be sure to give it a name you can remember, in case it ends up in a folder you didn't intend. And be sure to keep the file type ".txt" but not the asterisk.

(4) "And the D drive had the Windows and user folders not C so I used D:"

Very good. Here is how to fix that. Manually switch the letters once. This presumes, of course, that List Vol shows C:\ & D:\ get switched as before...

(a) Shift+Restart for the recovery environment.

(b) "Troubleshoot > Advanced Options > Command Prompt"

(c) Enter...

DiskPart

List  Vol <<< This shows the volumes with their drive letters.

                                            I will use "x" & "y", you must use the actual numbers.

Select  Vol  x              <<<  Select the one that has the letter "C".

Remove  Letter=C      <<< Removes the letter "C".

List  Vol  <<< You should see "C" is gone.

Select  Vol  y              <<<  Select the one that has the letter "D".

Remove  Letter=D     <<< Removes the letter "D".

List  Vol  <<< You should see "D" is gone.

Assign  Letter=C        <<< What was "D" is now "C".

List  Vol  <<< You should see "C" is added.

Select  Vol  x               <<< Goes back to "x".

Assign  Letter=D         <<< What was "C" is now "D".

List  Vol                        <<< You should see the letters have switched.

Exit

(d) Exit the Command Prompt with its "X" or type "Exit".

(e) Click "Continue" to get back to Windows.

After doing that once, the next time you go into the recovery environment, you should see they won't have switched again. At least, they haven't switched back for me. It is strange -- when I boot to my internal 1909 recovery environment -- a letter is added to my Recovery drive. It doesn't show up in Windows. And it doesn't show up in the external 1909 environment. But it was getting the letter "C" & Windows was changed to "E". But I switched them to normal, & they've stayed switched.

Edit:  Yep -- it's still holding...

Microsoft Windows [Version 10.0.18362.175]

(c) 2019 Microsoft Corporation. All rights reserved.

X:\windows\system32>diskpart

Microsoft DiskPart version 10.0.18362.1

Copyright (C) Microsoft Corporation.

On computer: MININT-ORVBH16

DISKPART> list vol

  Volume ###  Ltr  Label               Fs         Type             Size        Status      Info

  ----------       ---  --------------  -------   -------------  -------   ---------   --------

  Volume 0       E                                        DVD-ROM         0 B   No Media

  Volume 1       C   PCR Hard        NTFS     Partition      930 GB   Healthy

  Volume 2       F   WinRE 1909     NTFS     Partition      847 MB  Healthy

  Volume 3            ESP                  FAT32    Partition        99 MB  Healthy    Hidden

  Volume 4      D   ESD-USB1909  FAT32    Removable    14 GB   Healthy

DISKPART>

Windows (C:) still has its C: in the internal recovery environment. WinRE 1909 got bumped to F: because my 1909 Installation USB (ESD-USB 1909) was plugged in. When I then booted to the USB's external environment, WinRE 1909 had no letter, the USB was D: -- & C: still was C:.

OK. That's something to work with. But...

One thing: Your prior post sounds like you've got the Built-In Administrator account turned ON. That's really for temporary use in an emergency. It isn't full-functioning. Are you doing these update attempts while signed into that? You should sign into your user account instead, which preferably should also be an Administrator account.

Don't turn**off the Built-In Administrator, though, unless you've got at least one normal Administrator account. Either make the existing user account an Administrator or create a new one. Then, turn off the Built-In one. Need instructions?

Edit:  I'm having trouble understanding that SetupDiag report. Some of what I find on it is scary to suggest. I think we should fix the drive letter problem & resolve the Administrator account issue. Ensure we have a normal Administrator account, then run the upgrade again. But run it from the USB drive instead of through Windows Update. To do that...

Plug it in, open it in File Explorer, & click "Setup.exe". Run this way, it will ask whether to keep files & apps. Be sure to say yes. If it fails, post the new SetupDiagResults.log.

Here's what Setup Diag result's log.

Matching Profile found: FindAbruptDownlevelFailure - 55882B1A-DA3E-408A-9076-23B22A0472BD

SetupDiag version: 1.6.0.0

System Information:

    Machine Name = MYPC

    Manufacturer = Hewlett-Packard

    Model = 21-h013w

    HostOSArchitecture = x64

    FirmwareType = UEFI

    BiosReleaseDate = 20140616000000.000000+000

    BiosVendor = 80.10

    BiosVersion = 80.10

    HostOSVersion = 10.0.17763

    HostOSBuildString = 17763.1.amd64fre.rs5_release.180914-1434

    TargetOSBuildString = 10.0.18362.770 (19h1_release_svc_prod1.200309-1836)

    HostOSLanguageId =

    HostOSEdition = Core

    RegisteredAV = Windows Defender

    FilterDrivers = FileInfo

    UpgradeStartTime = 5/5/2020 3:31:35 PM

    UpgradeEndTime = 5/5/2020 4:43:01 PM

    UpgradeElapsedTime = 01:11:26

    CV = tFmz9P/b8E2yPqUB

    ReportId = F0D3CCB9-6371-48A0-AE2E-8679485A4EE3

Error: SetupDiag reports abrupt down-level failure.

Last Operation: Finalize

Error: 0x8007007E - 0x50015

LogEntry: 2020-05-05 16:41:26, Error                 DISM   DISM Driver Manager: PID=18924 TID=20744 Failed trying to load drvstore.dll - CDmiApi::InternalInitialize(hr:0x8007007e)

Refer to "https://docs.microsoft.com/en-us/windows/desktop/Debug/system-error-codes" for error information.

Last Setup Phase:

Phase Name: Pre-Finalize

    Phase Started: 5/5/2020 4:39:25 PM

    Phase Ended: 1/1/0001 12:00:00 AM

    Phase Time Delta: 00:00:00

    Completed Successfully? False

Last Setup Operation:

Operation Name: Process Drivers for Migration

    Operation Started: 5/5/2020 4:41:18 PM

    Operation Ended: 1/1/0001 12:00:00 AM

    Operation Time Delta: 0:00:00:00.0000000

    Completed Successfully? False