How to fix Windows 10 upgrade fail system error api-ms-win-core-libraryloader-l1-1-1.dll is missing
if you get an error: Windows10UpgraderApp.exe - System error
The program can't start because
api-ms-win-core-libraryloader-l1-1-1.dll is missing from your computer. Try reinstalling the program to fix this problem.
Here is what you need to do:
Replace C:\Windows10Upgrade\wimgapi.dll with file
located here: c:\Windows\System32\wimgapi.dll
Good luck!