Re: " someone wrote a program to swing the heads on one of those old giant hard drives back and forth. At the right frequency...cause the drive to walk away"

On some TRS-80 models I discovered a certain POKE command would make the screen flash, click, and "bounce" the image, similar to a power spike. So in the university lab I wrote up a small BASIC script with a delay timer to repeat "DANGER: Computer Overheating!" as the clicking/flickering increased in rate. I stood back to watch and waited for the timer to kick in. Nearby students would freak out. When the script was done, it deleted itself in case they got the lab assistant to come over. I was a stinker.