yes I also had a similar issue:
On my netbook: 1.6ghz atom, 2gb ram, GMA950, it ran fine in media player, but other players had trouble.
I don't know maybe windows media player is built with better hardware acceleration, or some special codec or something...
I never bothered with anything other than media player since windows 7 since it plays everything.
i want to learn something about graphics(cards,gpu,etc.), please guide me ... like asking me to read a particular thread(which u will tell me, which one to read).
help me in any other form... i just want to get some knowledge about that