Fix for Windows 10 Upgrade Assistant error api-ms-win-core-libraryloader-l1-1-1.dll

[German]Microsoft offers the Windows 10 Upgrade Assistant, which allows you to upgrade a system running Windows 7/8.1 to Windows 10. Now a new bug let the upgrade wizard fail due to a api-ms-win-core-libraryloader-l1-1-1. dll. Here is a fix.


The Windows 10 Upgrade Assistant allows you to upgrade a Windows 7/8.1 installation to Windows 10 and is described here at Microsoft. This possibility of a (free) upgrade should expire on 31.12.2017. Now blog reader Karl has reported a new problem with Windows 10 Upgrade Assistant.

There is a brand-new[ error] in the Windows 10 upgrade assistant which is officially terminates on 31.12.

Windows 10 Upgrade App-Fehler

Took me a few hours to find the solution. At the beginning of December the wizard still works. Now since mid-December the assistant stalls with an error. Also the Assistant’s GUI is now mixed between English and German.

api-ms-win-core-libraryloader-l1-1-1.dll missing

Searching the web for ‘api-ms-win-core-libraryloader-l1-1-1.dll is missing’ results in several hits from mid of December 2017. At Microsoft Answers there is a thread from December 19, 2017, dealing with this issue:

the program can’t start because api-ms-win-core-libraryloader-l1-1-1.ddl is missing from your computer. Try reinstalling the program to fix this problem.

There are a number of people reporting the same problem. The Upgrade Assistant has not been in working since mid-December 2017. At, someone posted a solution.

1. Terminate the Windows 10 Upgrade Assistant (close the error dialog).


2. Open file explorer and go to folder C:\Windows\System32\ and right click the file wimgapi.dll and select the context menu command Copy.

3. Then navigate in Explorer to the folder C:\Windows10Upgrade\ and paste the file (right click in folder without selecting any files and select the context menu command Paste).

Choose to overwrite the existing file on the option box that pops up. Rerun the Windows 10 Upgrade software to continue upgrading.The solution has been also presented at YouTube: How to fix api-ms-win-core-libraryloader-l1-1-1.dll is missing while upgrading to Windows 10.


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6 Responses to Fix for Windows 10 Upgrade Assistant error api-ms-win-core-libraryloader-l1-1-1.dll

  1. Mandy says:

    Thanks so much this worked like a charm!

  2. Josef says:

    Just wanted to say that the workaround did the trick an a Windows 7 Home Pr. SP1 64bit (english version) upgrade too.
    Thanks for posting this fix.

  3. Thomas says:

    Great fix, worked as advertised, easy and fast. Thanks for sharing.

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  5. aaa says:

    Thank you!!

  6. simon says:

    great! you are amazing!

  7. Samuel says:

    i can’t find windows 10 upgrade in my drive c, what can i do?

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