Resolved displayport to HDMI - sound but no picture

I just got a displayport to HDMI cable to connect my mother's computer with her big screen tv. I hear the sound, but the only picture I see is the icons in the taskbar. The other icons don't show up. The movie I played only transmitted the sound, not the video. There seems to be another option showing on both the tv and the computer that is labeled "ReadyDLNA:C3700-100NAS" yet I can't seem to move her movies into the video folder that exists there. Sometimes the mouse cursor shows up on the tv and can be moved. Please help me set this up.

 

OK, here is what works...
Choose HDMI source on where you want the movie to be viewed.
Right click on the video
Choose "cast to device" then choose "device"
Choose "Allow" on the receiving device when it asks for permission.
Watch the movie.