I use win xp pro, and I just installed Windows Media Player, but why the player stop playing in full-screen mode? It's ok minutes ago. I know this question is kind of stupid, any one knows how to fix it.
It is a feature of Windows Media Player, not a fault
It will automatically pause when manually selecting "Full Screen" (I suspect just to allow you to get ready)
You then need to press "Play" to play it again
Can I also suggest that you try another Media Player > Free VLC Media Player
It does an excellent job at playing most movies (anyway, much more than WMP) And is very easy to use, and I use it