I think the problem is that the nVidia 6200 video card isn't powerful enough to cope with HD playback under MP - press Shift+1 on the keyboard to show the rendering stats.
MP basically uses 3D rendering for both the GUI and video playback, so it needs a higher performance video card than MPC-HC (note your MPC-HC graph is using the overlay mixer, not VMR9 or EVR).
Have a look at
1080i material not deinterlacing under 1.0.1.0 - you probably need to be think about an ATi 4550 or nVidia 9400GT for HD playback.
Tony