We're pretty sure it's not a hardware issue because you are able to play some sounds. I'm starting to think it's an issue with one of the players. (Windows Media Player, Realplayer, VLC, etc.) Might also be a codec missing. Is it a DVX video? If it is, you can download the codec without having to install their player.
One of the things you can try is to remove media players one at a time until Windows Media Player is the only one left. If you're worried about losing the software, just dump the ones that are easily replaced. Like Realplayer, and VLC player.
If you're a fan of Apple, you might want to skip the next part.
One last thought. Do you use I-Tunes? I-Tunes and Quicktime will convert your files to a format that can only be played in their players. Apple makes nice hardware but their software is hideous! I had a brand new netbook with a ton of my music on it. I loaded I-Tunes onto it so I could load an I-Pod for my son before he deployed. It converted ALL of my muic files and filled my drive with duplicates! It took an entire weekend to convert it all back. Part of the problem was that my machine kept crashing. Since removing I-Tunes, my netbook hasn't had a single problem. It's the number one reason I will never own any of their products!
