I think I've killed my Macbook.

Was working all fine and dandy last night when I shut it down, etc. Then this morning I turned it on, it made the "aaaaaaahhh" startup noise thing, but the screen just stays white and nothing else happens.

Anyone got any ideas? I don't know what to do.
also, I didn't take out the apple cover plan thing. because I'm silly, maybe. I didn't think it would break! I've not even had it very long.

so in conclusion, :(