The only thing to do with a massive hard drive: fill it up with (part of) your CD collection. I derive a certain amount of pleasure from seeing xmms total up the amount of music available - I could presently play music for four days straight without repeating a song, should that need ever arise.

Doing this is also a nice stroll down musical memory lane - I remember playing Bob Mould's Black Sheets of Rain constantly in my early 20s. It's the angriest sad record I know.