My computer is a Dell Inspiron I 1520 that I purchased three or four years ago. Whatever sound card I have came with the computer. How do I determine what I have? I looked under control panel, sounds and audio devices. Sigma Tel High Definition Audio CODEC, whatever that means. I wish I could have someone sitting here next to me. Probably be able to diagnose instantly!!! Last night I went back at it again. Was able to add music tracks and nsound effect tracks no problem. Was playing back, adding here there and everywhere, then, for some reason, in the timeline mode everything disappeared - I still had the pink video, music and sfx boxes showing, but everything to the right, all the tracks, were gone - poof. Shut everything down in frustration. Just opened it up again this am. Timeline stuff back so decided to try to play from first panel in storyline mode. Everything going well through the first music track. When it got to the first sound effect track, no sound.