I've had my macbook for a little over a year now and I've never had a single problem with it until last night. After a program froze and force quitting wasn't working I shut my laptop down, when I started it back up it was in the grey screen mode for a long time before flashing a dark grey folder symbol with a question mark in the middle. Now, after a few more shutting down and restarting it doesn't even do that anymore, it's just stuck on a grey screen perpetually and won't go any further. Any ideas on what I can do to fix this without taking it to a repair shop? Any input is appreciated thanks.