My computer was running super slow and I was getting a spinning wheel on literally every application, including finder, so I turned it off to see if that would fix it. After that, every time I've tried to turn it on, it makes the startup sound, the apple logo comes up, a buffer wheel under that, and a progress bar under that. The progress bar always gets up to about an eighth of the way, then it disappears and the Mac turns off. It has Mavericks I believe. Can anyone help me out in a way that wouldn't cost me any money? I'm flat broke.