I suggest that you sell everything you own and pay for as much of it as you can, and try and get your parents to pay for the rest. If it means that much to you, it shouldn't trouble you to sell everything. I'm getting married in the middle of November and sold my entire computer collection (at a sizable loss, natch) in order to afford it. If you want it, you'll pay for it -- that simple.
There are some pretty ridiculous comments on this thread. "If you want to be popular, don't buy an iBook, give handjobs under the the bleachers during pep rallies!" Stop being so damn condescending. A hobby's a hobby, and if he wants to use a damn computer instead of joining a bunch of latent homosexuals in playing an idiotic game of freeze-tag with a big leather inflated egg, it's his right. Just shut the hell up and answer his question and stop trying to make amends for your wasted childhood.
Damn. Someone wants to be an actor, noone complains when he spends all his time acting. Someone wants to be a musician, they admire his dedication. Someone wants to be an athlete, they appreciate his athleticism. But if he wants to do something with a computer, they tell him to shut the hell up and go rake the leaves.