ooh, luckily i had my macbook user guide in my bag i bring to work...
one of the things it says for a laptop that won't start is to:
insert disk 1 of the install disks that came with the comp,
restart and hold C as it starts up,
choose installer > open disk utility,
follow instructions in first aid to see if the disk needs to be, or can be repaired.
worth a shot anyway.