I don't know about the connection with Windows 10, but whenever we had
problems with movies in E-Prime we found it to be the result of codecs.
In some cases we solved it by transcoding our movie files using
ffmpeg. You might also try using the CodecConfig utility that comes
with E-Prime. Try searching this Group with terms like "codec" and
"codecs" for more discussion. (And before it comes up again, wmv is a
container format, not a codec, there is a difference. And just because
a movie works fine in Windows Media Player or whatever does *not* mean
that E-Prime can handle it, E-Prime imposes more stringent requirements
because of the need for millisecond control.)
-- David McFarlane