How to Reset a Macbook
All MacBook models contain parameter random access memory (PRAM) and nonvolatile RAM (NVRAM). The PRAM of a MacBook includes your start-up disk, virtual memory, RAM disk, disk cache and other hardware memory features. If something goes wrong with your computer and you don’t want to lose your memory, check your warranty with Apple support to fix the problem. Reset your computer, however, if you plan to sell it or want to wipe the memory clean for any reason.
Things You'll Need
Close out of all of your programs, and the click on the Apple icon. Click “Shut Down” option on the menu that appears, and allow your computer to completely turn off.
Hold down the “P” and “R” keys before you turn your computer back on, and hold them down before the desktop appears.
Turn on the computer, still holding down the “P” and “R” keys.
Continue pressing the keys until your computer restarts and then turns on for a second time. Remove your fingers from the keys once you hear the system start-up sound.
Look through your hard drive to make sure all setting have fully reset. Repeat the above steps if your MacBook still needs resetting. Also, go to your clock and reset your time manually if necessary.