The problem isn't in the PC, that's why the mute or volume controls aren't doing anything.
You were on the right track checking for bad connections. Somewhere the wiring running to the speakers is just able to act as a reciever. You'd be surprised how little it can require to make a basic reciever in some situations. Basically a piece of wire to act as an antenna and a bad connection to act as a diode hooked up in just the right way and it happens. It's usually AM channels, but it can happen with FM too (AM is a simpler format to recieve).
If worst comes to worst, try some tin-foil wrapped around the wires to act as a sheild.
Right after collage, a friend of mine worked at a small radio staion in Indiana. They had the transmitter on-site, and in the building EVERYTHING acted like a reciever. They became very creative at shielding stuff, but never got rid of it entierly.
Me, I just thought it would be cool to climb the tower. Never got the balls to go more than about 75 feet though...Don't know what I though I was going to see up there anyway. One corn field pretty much looks like another...
Don
'01 22 Classic, 502/B1
And a bunch of other stuff
"If everything seems under control, you're just not going fast enough" - Mario Andretti