My Mac won’t start
I’ve got a flashing question mark
The flashing question mark folder is a sign that your Mac is having trouble locating its system folder. If you boot from an external disk, check it’s powered on and connected.
If you boot from your Mac’s internal drive, power it down and on again while holding down å. When the startup manager appears, if you see your startup disk in the options, select it. If that doesn’t work, repeat the process but this time select Recovery HD from the startup manager. Your Mac should now boot from its recovery partition. Select Disk Utility from the Utilities menu. When it opens, choose your startup disk and then click the First Aid tab. Click Repair to verify and repair the disk and then try and start up normally. Still no joy? You’ll need to start up again from the Recovery partition and reinstall OS X.