The two common power saving options in the Windows XP operating system are Hibernate and Stand By. Aside from the fact both power saving options help to conserve batteries, there are little differences between the two. When you go for Stand By option, the system's power consumption will be reduced almost to zero.
This only brings the computer to the 'on' state and also makes other applications, hard drives, and other essential properties of the computer to stop functioning. The problem with Stand By option is that you risk losing all the unsaved files in the memory.
However, in the event that you decide to go for Hibernate mode, it will help you conserve your computer's battery without losing the contents of the memory. When you select this option, all the files on the hard disk will be saved before your computer turns off. Another difference is that Stand By mode does not save more power like the Hibernate mode.