QUOTE(RHPConsult @ Sep 30 2003, 6:02 PM)
Zapping, in essence restores settings in Control Panels to those established "at the factory", those you had when you installed the OS right out of the box....I really applies to OSes < X.
More specifically:
"PRAM" stands for "Parameter RAM." It is a special place inside your computer where certain settings are kept. These settings include the current date and time, the address of the chosen startup disk, the status of the network, the address of the hardware devices the network is connected to, and so on.
It applies to any OS, including OS X. Some of these settings are specified using control panels in classic MacOS. In OS X, you set these settings using Preferences panels. The settings are often used by the computer's hardware (such as the network settings).
If the information in the PRAM becomes corrupt, you may have strange problems. The computer may "forget" what hard drive to boot from. It may "forget" what network device to use, or try to use some network device that does not exist.
Sometimes, when the computer behaves strangely, it's because the settings in PRAM are garbled or incomprehensible; that's when zapping the PRAM helps.