Since I just got a new job, I'm considering upgrading to a different Mac (most likely 15" PowerBook). I'd like to sell on eBay, but I'm concerned about any information that might be left on my hard drive after a clean install. What would be the best way to prepare my computer for a sale to a stranger? Is a program like SuperScrubber really necessary (I'd prefer not to have to buy a program just for this task), or are there ways to do it within OS X? Thanks in advance.