Win 10 "losing" boot partition - assigning wrong letter - can't boot

spunk said:

USE EasyBCD to fix your Windows 10 install in your Multi Boot computer

Hi, Spunk -
Per their website, EasyBCD can't fix a non-bootable Windows install - apparently it's only for bootloader management. However, they're happy to sell you something called EasyRE for $20-40 ;-)

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Try3 said:

Bob,



When you boot into any recovery environment [including from the USB], you are in a different OS and it assigns drive letters according to its own rules. Those drive letters are used only while that temporary OS is in use. As soon as you are back in normal Windows your drive letters will be decided by Windows again so you'll be back to the drive with Windows on it being C:\. You do not need to take any action about this matter.



If you were activated before then the MS servers will recognise your computer when you go back online afterwards and will activate you again. There is no need for any product key or indeed any action on your part - during any reinstallation you just skip the product key step.


System restore points are only marginally more usefu than chocolate teapots. Put your faith in system images instead.

Denis

Denis - thanks very much for the comeback. Much appreciated. Yes, agreed, chocolate teapots are not very functional!

Thanks everyone. Reinstall complete (except for Quicken 2017, which wouldn't re-install, which I suspect is a ploy by Intuit to get me to buy the new version).

All's well, and backed up. Much appreciated!

Bob

Thought I'd add my experience since I recently went through this twice.
This solution doesn't require reinstalling, it's pretty fast, and it's not likely to delete any of your data.
Here's the short version:
* Use diskpart to correct your drive-letter assignment
* Run Bcdboot c:\Windows
* Log into Windows and figure out how to get the update to install without trashing your boot process

TL;DR;
My drive letters were also incorrectly assigned after an update, which I determined was the cause by looking at the drive and drive-letter info in diskpart (list volume) and also by looking at the content of each drive with the dir command.
Then in diskpart I corrected the drive letter assignments. I had to bump an unused partition off of one of the drive letters first so that I could use the letter for another drive.

To set drive letter in diskpart, run:
List volume (to see the drive letters and volumes)
Select volume X (where X is the number of the volume from the list above that you want to change)
Assign letter=# (where # is the letter)

Once you have fixed all the drive letters you need to fix, you'll see they're fixed in the command line interface, but if you just reboot now they will get mixed up again.
I ran the following three command but I'm not sure they're necessary; including them just in case:

Bootsect/nt60 sys
Bootrec /fixboot
bootrec /rebuildbcd

After that I ran:

Bcdboot c:\Windows

(Obviously change that if your copy of Windows is on a different drive)
After this step I got the message "BFSVC warning: failed to remove duplicate object from bootMGR display order. Status = [c0000225]
Boot files successfully created."
The first part sounds like an error, but don't work about it.
Type exit and you should get back to a blue screen that now gives you the option to restart in Windows 10. I had to manually restart once after this when my pc got stuck at the EFI screen, but after that I was able to log in like nothing happened. The update still hasn't applied, but I was able to get back to work without having to reinstall anything.

Good luck!