Q: MacBook Air will not boot.

Ok so I turned off my MacBook Air last night and turned it back on this morning and all I'm getting is the grey screen with the apple logo and spinning wheel. I have tried rebooting in safe mode and it does nothing. Tried repairing the disk then restarting it and still nothing. I noticed in the disk utility it says that the Macintosh HD is not mounted. Is that what is causing the problem? I have tried everything on here short of wiping the computer and starting over.