Hard-drive based media players aren't anything new, but hifi equipment actually built from old drives are somewhat rarer. At Hifiduino they're using an Arduino microprocessor to construct a DIY preamp, and they've salvaged a deceased hard-drive to form the base and the top.
The Arduino itself is actually detachable from the internal chassis, with the individual connections being made to a custom "shield" board. That allows the microprocessor to be removed and connected up to a computer for easy reprogramming.
Obviously this is just the case - the rest of the Hifiduino project deals with turning the board into a DAC with a rotary control, 4 x 20 LCD display and remote control for volume - but it's a good looking case and that's reason enough for us. The only thing which might have made it better is actually using an old hard-drive platter for the rotary control, rather than the machined knob.