To begin the process of unlocking the MacBook you should hold for a few seconds. If the computer does not start, turn it off by holding the power button (0) for about 8 to 10 seconds.
Disconnect all external peripherals MacBook to unlock and try restarting by pressing the power button (0) hold down the Option key.
Once you have booted the MacBook, click the hard disk icon () and then the right arrow.
Next, open System Preferences and click Startup Disk.
Select a local folder system Mac OS X.
If the problem occurs frequently, you may need to reinstall the software
Mac system.