Oh, and back in a college before there was a such thing as "accounts" on a PC, I wrote a little
VB program that would randomly pop up windows with fake error messages.
The problem was that my friends would do things like change the background on my PC to porn pictures (really bizarre stuff) and mess with settings. I also noticed that they would stop using my computer when they thought they broke something. So if I set up a fake error to appear after 45 minutes, it would usually stop them in their tracks from messing with stuff after they finished writing a paper...