NOTE: Resetting the PRAM may require you to set some settings such as mouse speed and keyboard rates again. Allow it to cycle a couple of times and release the keys and allow the computer to boot normally. The computer will chime, and then continually reset and chime while these keys are held. To reset the PRAM, reboot the computer and hold the options-command-P-R keys at the same time. If these settings constantly get reset even when you have not manually reset the PRAM, the computer's logic board battery may need replacing. It is possible that settings in the PRAM may indirectly affect various system functions like the spell checker, but knowing this is anyone's guess. Sometimes there have been odd problems that have been cured by PRAM resets, including one reported on recently by MacFixIt regarding spell-checking not working. Prior to OS X, the PRAM held information for networking, but that has been removed so any network troubles should not be affected by PRAM settings. Mouse input rates (click and tracking speeds).Boot volume isn't set (question mark shows briefly before booting).Time zone information and clock settings.Video resolutions not sticking or not all available.If you have problems with any of the following then a PRAM reset might help you out: As such, it's not necessarily bad for the computer, but may lead to customized settings such as alternate boot devices and speaker volumes being put back at default values. Resetting the PRAM may sound like an exotic fix that somehow may magically cure something however, many times doing this is just a shot in the dark. Many times when people's computers get bogged down and they are experiencing problems, advice will be given to "Reset the PRAM." In certain situations this can fix things, but many times people just blindly throw that advice out there. There is a small battery on the computer's mainboard that helps maintain the PRAM settings when power is off. The Parameter RAM is a small amount of "nonvolatile" RAM (NVRAM) that holds various settings that the system can use before the operating system loads, and maintains these settings even when the computer is turned off.