"Here are some examples: you might use the planets in the solar system (I would never do this; who wants to have to wait for the discovery of new planets to buy your 9th computer?)"

For this reason, I use moons of our solar system in naming external hard drives at home. Figure it will last me a little longer, and saves me having to say to my wife in front of friends "Can you put the wedding photos on x?" and "Is x now full?" for certain instances of x towards the outer reaches of the system.