If it was off or asleep there is a good chance you may have just jostled the hard drive, and it simply needs to be reseated. This happened to my girlfriend's MacBook.. more than once. If it was on and in use.. well you may be out of luck.
If it is a white MacBook, reseating the drive will be easy. Just remove the battery, remove the metal retainer which covers the RAM slots, then pull out the hard drive by the plastic tab and firmly push it back in. If you are lucky, this will solve your problem.
However the squeaking noise you described does not sound promising.