I found an old archive of emails involving computer horror stories: backups gone bad, deleting the wrong files, and so forth.
Somewhere along the line, somebody asked for the more Stephen King-ish style horror stories, about the system clock running backwards, files undeleting themselves, and so forth. That lead to this anecdote:
Many years ago a tiny little college in the middle of nowhere purchased an NCR tower, then a newfangled contraption. A half-dozen of us were using it for an assembly class. The prof should have made his warnings about TRAP a little more clear. One student runs his program and it suddenly begans spawning processes, rapidly filling the machine. The prof came in, amused, logged on as superuser, and killed a process. Another process was immediately spawned. The prof tried again. He was ignored. He was also no longer amused. After several minutes he gave up and turned off the box. The tower didn't even flinch. He pulled the plug. Nothing. He ripped the back off the box and dug around. Finally he found the fuse and pulled it, killing the machine.
Some of us later claimed we heard laughter as it went down.
(Many times since then I have wished other computers came with a backup battery as standard issue.)