I fucked up someones computer.
Changed the loading screen to goatse, and made it so the start up music was someone yelling "BOB SAGET!!!". I then removed all the icons, placed a folder called "Child Pornography" took a screen shit, deleted the folder, but the shortcuts back,used the screen shot as the background.
I then corrupted all of his game files.
That's the best I've ever done. Sadly. I need some work.