1. Reinstall Windows Media Player

2. Defrag the hard drives (you'd be surprised)

3. Make a list of every audio and video device (hardware and software) that you use. Then go over them one at a time and check for update and drivers on the web. I know I've said that before but checking every two weeks or so isn't out of the ordinary.

I hope this helps...

Honestly, whenever I've had a problem with a video file or a sound file, 90% of the problem has to do with a driver or a codec. The other 10% is when I open up the case and find something loose.