<p>In order for most people to install OpenLP on Windows, we have to compile and build it so that Python, Qt and all the other it needs are built it. When you run OpenLP from a testing or development environment, it is running "natively" - i.e. without any bundling. This could be the reason.</p>
<p>That said, a fair number of folks have had success playing videos using the Windows build. I cannot say why or what their setup is, as I use Linux, but maybe someone else who runs Windows can comment and tell you what they did.</p>