Just experienced a hard drive failure right now on my MacBook (2007). Everything had froze and I shut it down. When I started it again, the screen was dimmed and the Apple jingle went on a louder sound then before. Is this a sure sign of a MacBook hard drive failure or would it be related to something else, for example, the logic board? Also, what should I do now? Last full backup was 3 weeks ago and I had worked on lots of things between that period of time and now.