zapping PRAM

PRAM stores certain system and device settings in a location that Mac OS X can access quickly. Exactly which settings are stored in the computer's PRAM varies depending on the type of computer as well as the types of devices and drives connected to the computer.

Some information stored in PRAM includes:
Time zone setting
Startup volume choice
Speaker volume
Recent kernel panic information, if any
DVD region setting

esetting PRAM and NVRAM

1. Shut down the computer.
2. Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

Your computer's PRAM and the NVRAM are reset to the default values. The clock settings may be reset to a default date on some models

 

No, you just do it when you see problems. As opposed to repairing permissions, which you should do every couple weeks or so.