Energy Saver sleep settings
Energy Saver sleep settings on PCI-based Macintosh computers are stored in the Energy Saver Preferences file, not parameter RAM (PRAM). The Energy Saver Preferences file is located in the Preferences folder within the System Folder.
Energy Saver default sleep time
Moving or discarding the Energy Saver Preference file and restarting the computer resets the Energy Saver control panel to the default sleep time of 30 minutes.
Additional information
With some Mac OS versions, the Energy Saver control panel may place an alias of itself in the Startup Items folder if no preference file exists. Once the control panel is opened, the alias is removed from the Startup Items folder and a preference file is created. Mac OS 9 and later creates a default preference file without opening the control panel at system startup time.