When I turn on the MacBook, I get the startup tone, the apple logo on a grey screen and the spinning gear.
But the MacBook never starts up.
I've tried starting from Safe Mode, but it still just gets to the apple logo on a grey screen, with a forever spinning gear.
Press Command and R keys when your Mac starts, open Disk Utility and verify the drive. If there's an issue, repair the disk
Retrieving data ...