A very simple to do mod with an outstanding effect!
Also a good way to get some soldering experience and make use of all those extra hard drives from the IDE days!
Instructions + Demonstration
In summary, you solder some wires to some places on the hard drive and ghetto-rig the wire up to some speakers (unless you have a headphone jack) and
>BOOSH!< you have some geek-speakers.
MORE INSTRUCTIONS HERE!