My Media player 11 video playback works for the first 10% of the video, then all goes black, but the audio is still there
Try using it 1/2 screen or 3/4 screen, don't use it full screen. The problem being that the CPU cache is being overloaded. When the CPU goes 100% the screen goes black. The CPU cannot handle all the information. If you play back with a smaller screen, the load is reduced on the CPU.
If you were using a quad core processor, the CPU would not overload. Your smaller CPU just does not have enough cache memory.
New video applications demand bigger CPU capabilities, the older CPUs just can't do it all anymore. That is the reason for the new dual core and quad core processors.
No, installing a separate video card does not fix that problem. You have to upgrade the motherboard and processor.