I had the same problem. I have a Dell Dimension 4550. My sound board is integrated to my motherboard. The sound slowly started to cut out after I replaced my OEM graphics card with a new more powerful card. After I did some research on the net, I found out that my OEM power supply may not be powerful enough to handle all the add-ons that I added (new graphics card, DVD burner, more memory, second hard drive). My OEM power supply was 250 watts, so I updated to a 450 watt model and the sound problem stopped. I'm no computer expert but, I figure that the graphics card was pulling so much juice while I was playing FS
that the power supply couldn't keep up.
It would help the "computer experts" here in the board if you could post your computer specs. That way they are better able to help you. Thanks