OS X :: Removal Of Irritating Continuous Music In The Audio Background?

I really hope somebody can help me with this. I've had an iMac for several months now. Before that I had a PC. Very soon after I bought it I started to get pounding rock music in the background whenever I tried to listen to anything. It's loud enough to overwhelm whatever it is I'm trying to hear. It isn't going all the time, but something seems to start it, and then it goes for days. I must have downloaded it accidentally when I was blundering around in the first month or os. If it was a PC I'd be able to find it, but Mac is still a mystery to me. I seem to remember that I downloaded something to do with a waterfall, "Dakota Falls" perhaps. The video was a waterfall which sat on the desktop. It looked quite pretty, but when I got rid of it the music wouldn't go away. So right now i can't listen t anything on my new iMac, and obviously I can't watch movie's or anything. It's really frustrating. The OS is Leopard. Also can anyone suggest a decent book on Mac that isn't too superficial. I'm not totally certain of the connection between the waterfall video and the pounding music, but they seemed to occur.