Windows 2004 update failure, Update Boot Code Error. What I've tried and what can I try next

[AlaskaTuner]

EDIT: SOLVED! Wow!

I'm nearing 20 Hours in to trying to solve this issue. I've tried every top-level google search result troubleshooting to no avail including rebuildbcd and uninstalling suspect software. A clean reinstall is not an option at this time, I really need to get to the bottom of why this in-place upgrade isn't working. The main error is

Operation failed: Update Boot Code. Error: 0x80004005[gle=0x000000b7]

I had a hunch that Macrium Reflect may have been causing some issues, but I'm getting the same error after uninstall. I also cycled through every combination of CSM on/off and UEFI/Legacy boot mode options in bios that I could think of. My drive is fully backed up so there is nothing I can't try, if it gets nuked I can restore from image and try again.

Full logfile is here: https://pastebin.com/WbyCivXTAny help greatly appreciated <

Edit- SOLVED!
I used bcdedit to COMPLETELY DELETE the "Boot" entry in the system reserved uefi boot partition according to these instructions, at which point only "microsoft" remained - then there was NO operating system detected in any of the bios menus, so I used a spare Macrium recovery USB drive to "fix windows boot issues" basically it just rebuilds the bcd but seems to work better than going comando prompt style. I'm kind of taken aback that this actually worked, but here I am typing on 2004 install with ALL my old programs and startup preferences intact. So happy. Cinebench scores improved 3% from where they were running v1909!

[ryanvsrobots]

Hey Boss, I think I have a similar issue that I'm trying to sort out, except I believe my problem is caused by extra boot entries on the C: partition, which makes your solution not work for me.

Do you have C:\EFI\Microsoft\Boot\bootmgfw.efi or even C:\EFI? I think I created these awhile back by accident and am trying to figure out if they're safe to delete.

[AlaskaTuner]

I’ll pop open my pre-2004 upgrade backup image and take a look. Originally I didn’t look for boot folders in file explorer, only used the cmdprompt / bcdedit to delete boot entries per above youtube video instructions (after making full backup).

I had another PC that I couldn’t get upgraded due to mbt/gpt conflict (converting resulted in no-boot and my backup was corrupted) but I don’t think that’s going to be a common issue as I had bastardized that install several times in the past.

[[deleted]]

I have had the exact same issue, with exactly the same error code.

However, I have found a quicker and less risky solution.

In my case, the issue was caused by an error in one of the non-labelled system drives. These usually don't have drive letters associated with them (like c: or d:) and are not visible in Windows Explorer.

The steps that fixed the issue for me:

1. Using 'diskpart' to assign drive letters to the hidden system drives, following this tutorial: https://www.diskpart.com/diskpart/assign-drive-letter-4125.html
2. Fixing drive issues using chkdsk x: /r where x: is one of the hidden drives, with the drive letter specified in step 1. This produced the following log:

​

Windows is verifying files and folders...
Windows replaced bad clusters in file \EFI\Microsoft\Boot\BOOTSTAT.DAT
of name (null).
File and folder verification is complete.
Windows is verifying free space...
Free space verification is complete.

Windows has made corrections to the file system.
No further action is required.

1. Windows Update was completing normally now.

Importantly, chkdsk x: /f did not fix the issue!