I made a *silly* program in C recently.
What it does is make noise on your computer, you know, those simple beeps that come from the CPU. Thing is, it keeps beeping and you cannot close the window or turn it off. You cannot end it's process from the task manager (ctrl-alt-delete) either! It's always labeled as "not responding"... And since we use WinXP in school, the only way my friends turned it off successfully was by logging out coz that way, the computer forces every program to shut down.
I'm sure some of you have created such a program too! But mine asks the user if he choose to run the program or safely quit it. Pretty irritating...