Tech mystery: New Dell, when online sound speeds increase, when offline sounds normal

This is a problem my mom is having with her new Dell. She says that when she is online all of her system sounds, music, etc, speed up…however, as soon as she’s offline the sounds play at a normal speed again. She asked me this because I’m usually pretty good at helping her out with computer issues…but this one has me baffled. I’m thinking it could be a driver issue. But I can’t think of any scenario that would cause this to happen while online. Any thoughts? (btw, she’s using XP)

What model Dell is it? A 4550? If she just bought it, it should be covered by their tech support line.