Media Element (WPF) is not working Windows 8

Revision 1
Hi,
I created a solution that contain both Windows application project and WPF project in the singe solution. Running this on Windows 8, i am getting a unknown error. That if start up project is Windows application, then the video is playing but its not visible. But If the start up project is WPF then the video is playing well. I know how its sounds like. But i am getting this problem. Please help me on this.. Thank you.