You could use the existing lines to send stereo audio to any room in your house. There are four wires so you can take a regular phone jack and splice it to a set of RCA cables then plug that into the output of your main stereo system. Then any other room in the house with a phone jack will have an available signal to tap in to with a similar spliced jack to the input of any speakers you want in there. The wiring isn't "beefy" enough to carry an amplified signal so you should use the amplified output on your main stereo and have a separate receiver in the other rooms. It's not going to sound as good as surround sound but it's great for parties. You can have multiple sets of speakers throughout the house running from the same stereo/room.

I agree about the freezer suggestion but you left out one VERY IMPORTANT precaution! The cold metal being re-exposed to a warmer environment with higher humidity when removed from the freezer will result in condensation on all external AND internal surfaces! The best way to do this safely is to put your internal drive into an external HD enclosure, connect the USB and power cord, then double bag it and tape the ends. You have to make the bag air tight but leave your cables hanging out. This way the drive is cooled with a fixed amount of air (and thus water particulate) surrounding it. As it cools a very small amount of moisture will be locked in the bag but not enough to be of concern. When it is removed from the freezer, this small amount of moisture is all it can/will be exposed to and further moisture from the surrounding air will be isolated. Once the drive has stabilized to ambient temperature it can be safely removed.