The Parameter RAM (PRAM) stores settings related to your computer's devices and settings, such as volume, display resolution, and startup disk. To reset your PRAM, follow the steps below:

  1. Turn off the system.
  2. Turn the system back on.
  3. Before the gray screen appears, press and hold Command, Option, P, and R.
  4. As you hold down the keys, the system will restart. Wait until you hear the startup chime for the second time, then release the keys.

Note: Resetting your system's PRAM may set preferences to default settings. You can use System Preferences to readjust your settings according to your preferences.