Just recently got back from a visit to my local Apple store in regards to a faulty power adapter. My Macbook started up fine at the store, as it has over the past two years. However, after getting home and trying to turn it on, the laptop fails to boot up. It sits at the grey screen with the Apple-logo and spinning progress circle, all while the fan starts to whirl as if my macbook were on fire. I've experienced a failed hard-drive before, so I know of the folder w/question mark screen, and this screen is not like that. I've also tried booting up in "Safe-Mode," but that won't work as well. I do have a start-up disk and external hard-drive... I'm just curious to see what other options I might have before reinstalling Leopard. Any thoughts?