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I was that 9 year old, and I can assure you I was bored. Another really 'funny' trick we used to pull off was to write a BASIC program that would sound a high ear-piercing tone. I would then add a line like
FOR A = 1 to 25000: NEXT
and then lock the computer (on a Commodore 64 you would do something like POKE 808,202) and run the program. I remember that I once leisurely descended the building from the 5th floor down (by the elevator), and heard my sound just as I reached the bottom level. Ah, those were the days.