Not very many people use their Task Scheduler and they should because it can really wind people up!

If you have access to someone's computer briefly whilst they are away, load up their Windows Task Scheduler (should be on the System Tray, it's a blue box thing with a clock and book on). Then, set it to load up loads of their different programs at various time intervals throughout the day! It's a time bomb of frustration and is the easiet way to wind anybody up.