Every once in a while my PowerBook beeps. One of those short beeps you hear on old DOS computers when they boot up is the best way I can describe it. I thought at first it was my PC since it has a built in speaker than can only beep, but I've heard it in many places from my laptop. When it beeps it beeps at different times: sometimes once during just general computer use, sometimes just once during startup. Any idea what to make of this? If the beeps were becoming more frequent I'd say it was a countdown to the explosion of my PowerBook, but so far they just seem to occur once or twice a month.