In a Mac computer, information about the computer’s configuration is stored in a type of memory called PRAM. The PRAM stores information about the computer’s power management settings, installed hard drives and other items. When a Mac laptop becomes stuck on the boot screen after being turned on, it is often caused by a problem with the PRAM. Reset your Mac laptop’s PRAM to its factory configuration to allow the computer to boot.
Resetting the PRAM in Newer Macs
1. Turn the computer completely off. Hold the power button to force it to shut off, if necessary.
2. Turn the computer back on.
3. Press the “Command,” “Option,” “P” and “R” keys on the keyboard simultaneously, and hold them down. Do this immediately after pressing the power button. After a few moments, the computer will restart, and you will hear the Mac start-up chime again. Release the keys, and the laptop should boot. If it does not, continue to the next section.
Note: On some Mac laptops, the Command key will have an Apple logo rather than the word “Command.”
Resetting the PRAM in Power PC-based Macs
4. Turn your laptop off completely. Press and hold the power button until you are brought to a command prompt. Note that this only works in Macs with Power PC processors and that most Power PC-based Macs should respond to the commands described in Section 1, making these steps unnecessary.
5. Type “reset-nvram” without the quotation marks at the command prompt and hit “Return.”
6. Type “reset-all” and hit “Return.” Your Mac should reboot on its own, and Mac OS should load successfully.