the most I managed so far was to reproduce the sound, without image
<MediaElement Name="myMediaElement" LoadedBehavior="Manual"
Margin="5"
Grid.Row="0"
Grid.Column="0"
ScrubbingEnabled="True"
Source="C:\Users\TheMagicTool Server\Downloads\myVideo.mp4"
/>
Does the video show up at all? Just a hunch, try adding Height="200" Visibility="Visible" to the MediaElement.
<MediaElement Name="myMediaElement" LoadedBehavior="Manual"
Height="200"
Visibility="Visible"
Margin="5"
Grid.Row="0"
Grid.Column="0"
ScrubbingEnabled="True"
Source="C:\Users\TheMagicTool Server\Downloads\myVideo.mp4"
/>
Not sure if this'll help at all but worth a shot. MP4 should be supported.