A Japanese company Lupo, is selling a computer case constructed entirely out of cardboard.
All you need to do is remove perforated sections of the cardboard into the respective parts, fold along the lines as directed, and - perfectly functional PC case that is "biodegradable". Need to add a new USB port for that dongle? Just whip out a box-cutter and you have it. I wonder what would happen if the CPU overheats and turns the case into a pile of ashes.
That's certainly thinking inside the box.