Use Standby Or Hibernate

Windows XP provides two battery-saving sleep modes for your computer: Stand By, which is kind of like snoozing; and Hibernate, which is deep, rapid-eye-movement-style slumber. Use Stand By for brief intervals when you won't need the computer--you're stretching your legs on a long flight, for instance. Hibernate is the ticket when you won't be using your computer for a while--you're changing planes at the airport, say--but you want to resume work faster than you could after a complete system shutdown.