Hi Catventure,
I am sorry you observe issues.
The winmm.dll is present on my Windows 10.
MCI stands for Media Control Interface and it is a "black box" provided by Windows:
https://docs.microsoft.com/en-us/win.../mci-reference
mciVideo.inc is a wrapper Mike prepared 12 years ago.
The error in playback can be caused by range of reasons - bad graphic driver, missing video codec, for example.
I think there is also an error in the... error handling part of mciVideo.inc:
The j is not declared. Please declare it as Int32/Long somewhere before the call.Code:j = mciGetErrorString(mvi,varptr(mvSReturn),sizeof(mvSReturn))
Then you should receive text error message from Microsoft, which may help you go further.
Petr