You can run linux on a mac.
But if you want a seperate computer for linux you can find lots of cheap pc parts at Pricewatch
or you can buy a lindows computer there only 200 bucks and faster then a P3. Or another option is you can surf around some thrift stores and pick up a old pc for CHEAP!! and some little computer shops hold some old PC parts in back they would probly be glad to sell you or maybe even let you have them for free if you just sit around and chit chat with them I did it.