Standby is a power-saving setting under Windows XP. Standby is not the same as shutting the computer off. It still requires power, and coming out of "Standby" is faster than the computer's full start-up process. Your computer may or may not have come pre-configured with a "Standby" time.
Click your "Start" button. Open the "Control Panel". Choose "Power Options."
Look at the "System Standby" setting on the "Power Schemes" tab. If this is set to "Never," choose to change to a power scheme that has a Standby time you like. If the setting is not at "Never," then Standby is set correctly and does not need restoring.
Click the down-arrow to the right of the setting and choose a length of time you'd like the computer to sit idle before going into Standby. "Standby" is not the same as "Hibernate". Click "OK." You may need to restart the computer before the new settings take effect.