Might be able to score a free one from your school or go dumpster diving. At my high school, there are always parts stacked up in the halls that you're allowed to take stuff from. Although most of the stuff is terribly, terribly old. If you know someone getting a new computer, ask if you can have their old one. Or do the same to any stores if you see that they're getting new equiptment. A lot of companies just throw them out or get them hauled away, just grab some of that.