I have windows xp professional service pack 3. Lately, whenever I try to open/play a music file such as mp3(configured to be played by windows media player)by selecting it and either pressing enter of double-clicking with the mouse button, nothing happens. But when I right-click and choose 'open with' > windows media player, it plays. I can also open th media player with no problem. I just can't open/play the music file by either pressing enter or double-clicking.