Hi, I'm Sadique. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.
Shut down the MAC > Plug in the MagSafe power adapter to a power source and connect it to your MAC.On the keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time and then release all the keys and the power button at the same time.Then press the power button to turn ON and immediately press and hold the Command-Option-P-R keys before the gray screen appears.Keep holding the keys down until the computer restarts and then release the keys.
Tell me if it makes any difference to your problem.