I have a 2007 Macbook and The other night i was using my laptop no problems at all. The only thing i had running was Adium and Entourage. I went next door to my roommates room and watch a movie and than i came back and i could not make the screensaver stop. I push space and moved the mouse and nothing happened and than i just shut it down by holding the power button and went to bed. Woke up the next morning and when i went to boot it up all i got was a gray screen and a folder icon with a question mark on it, that flashes. I tryed to reinstall Mac OS but it says that i have no hard drive, but i know i have one because i never took it out...Any ideas on how i can fix this?