As a bonus here is a very evil prank:
Find some icon on the desktop that is very important to your victim. In this example i use a game, but you can also use it for Internet Explorer or anything else. Move that icon somewhere on the disk drive so that it dissapears from the desktop.
Make a new shortcut and use the following text:
shutdown -s -t 60 -c "Windows has encountered a virus!ï»¿ To protect your data windows is shutting down."
You can use any kind of text you want of course. "This is an illegal copy of [game]" can also work wonders. You can also shorten the time by changing the number 60 to another number.
Now change the icon of the shortcut by going to the .exe file of your victims favourite game.
Rename the shortcut to the name of the game