Resetting PRAM and NVRAM on Power Macintosh and iMac

1. Shut down the computer.
2. Locate the following keys on your keyboard: Command, Option, P, and R.
You will need to hold these keys down simultaneously in step 3.
3. Press the Power button, then hold down the Command-Option-P-R key
combination. You must press this key combination before the gray screen appears.
4. Hold the keys down until the Macintosh restarts itself twice.
5. Release the keys after the Macintosh restarts twice.
6. The parameter RAM and the non-volatile RAM in your computer is reset to the default values. The clock setting are not changed.

Contents of PRAM Contents of Parameter RAM are as follows.

Some Macintosh computers may not have all the settings described below.
Status of AppleTalk Serial Port Configuration and Port definition
Alarm clock setting
Application font
Serial printer location
Autokey rate
Autokey dela
Speaker volume
Attention (beep) sound
Double-click time
Caret blink time (insertion point rate)
Mouse scaling (mouse speed)
Startup disk
Menu blink count
Monitor Depth
32 Bit addressing Virtual Memory Ram Disk
Disk Cache