Maybe I know.....
When I bought my new Dell computer, I kept my HP speakers. I went to play one of my games on my new kick-*** computer, and to my surprise the volume was so low I could barely hear anything. I went through all the options in Windows and in the game, tried with mp3 files, no luck. The problem turned out to be that the Dell soundcard didn't support non-self-amplified speakers. I.E., speakers that aren't separately plugged in to an outlet. I ended up buying a surround-sound speaker system at Wal-Mart for 30 bucks, plugged it in, plugged in my sound jack, and it works fine.