Yesterday, by accident, I discovered a rather odd feature of some Windows XP machines. Hold down the Alt Gr key and press the down arrow, and the display flips upside-down. Alt Gr + Up Arrow flips it back. On some machines (though not mine), the right and left arrows also have appropriate effects.
Does anyone know what the hell this is for? (Other than doing it to your colleagues' machines while they're at lunch, that is.)