Reducing Intereference in Your Speakers?

PolicyWonk asks: "I just bought a new stereo, a Sony CMT-EP707, into which I intend to plug my laptop when watching DVDs, and my iPod when listening to music. When I first turned the stereo on I was horrified to hear interference from a local radio station, as well as a general hum emanating from the speakers. The hum and the radio emissions are audible even when the stereo's volume is set to 'min' and irrespective of what setting the stereo is on (i.e. Tuner, CD, or MD), or what input is (or isn't) plugged into the stereo. (I have tried my laptop, iPod, and no input). That means that during a quiet pause in a movie, or the intro to a song, this background noise is clearly audible. No amount of moving the speakers around the room, or plugging the stereo into different grounded outlets seems to fix the problem. I've checked my outlets, and they appear to have a ground connection, but I live on the fifth story of a circa 1900 apartment building in Manhattan, so it's anyone's guess what happens to the wires once they are in the walls. Anyone have any good solutions for reducing or eliminating interference from nearby radio sources?"