This is a known problem with some 7 to 10 upgrades along with errors like this:
The short version of the solution seems to be:
Replace C:\Windows10Upgrade\wimgapi.dll with the one from C:\Windows\System32\wimgapi.dll
Copy C:\Windows\System32\wimgapi.dll and Paste it into C:\Windows10Upgrade replacing any existing file.
There is no Replace - use Paste instead and respond in the affirmative if asked to overwrite an existing file.
Here is one link with a solution:
Here is a recent topic in the Microsoft TechNet Windows 10 community that starts with many impossible to work ideas and false starts but eventually an idea is posted where several folks report success following that advice (I cannot validate, test or verify) so I suggest reading through the replies focusing on the replies where this idea worked:
On I side note I wonder:
If you are upgrading Windows 7 to Windows 10 and have run into a snag (which seems to have a workaround) what other snags are you going to run into later?
If the upgraded system malfunctions or has issues I would always be wondering if the problems had something to do with the upgrade process that did not go well.
If it was me and if I wanted a Windows 10 system I would create some Windows 10 installation media and perform a clean/fresh install from scratch instead of doing an upgrade. If you are having a problem like this right out of the chute what other problem lie ahead?
If you have an issue in the future that requires Windows 10 installation media to fix it what are you going to do (or do you have some Windows 10 installation media)?
Edited by joseibarra, 30 December 2017 - 12:06 PM.