So you need a computer. You’ve looked at the newest Dell XPS, maybe a spiffy HP Pavilion. You’ve surfed over to Apple’s Web store to drool over the powerful, stylish machines of Steve Jobs. But there’s a problem: You’re broke. You just don’t have — or shouldn’t be spending — the $600 to more than $2,000 you’d have to pay for one of those new digital hotrods.