Oh, shoot! My MacBook won't boot! Silver screen is all I see!

Try a PRAM reset:

1. Shut down your Mac.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

Any unusual noises coming from it?

Have you tried booting to your startup disc? (Hold Option on boot to access the startup manager, which will let you choose between internal HD and optical drive)