With me on Windows 7, it's in c:\windows\system32\compattel.
In c:\windows\winsxs there are 4 copies dated 23-08-2015 and 4 copies dated 20-12-2016.
My suggestion: search in winsxs and copy it to system32\compattel. Or copy it from another Windows PC (via a USB-stick).
Or maybe start with sfc /scannow to let Windows fix it itself (that's the way to repair corrupted or missing files).
How can I download for free api-ms-downlevel-user32-l1-1-o.dll

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