Windows XP has built-in support for hibernation (OS-controlled ACPI S4 sleep state). Hibernation saves the complete state of the computer and turns off the power. The computer appears to be off. This is the lowest power sleeping state available and is secure from power outages.
When you resume from a hibernated sleep state, the BIOS performs the normal POST, and then reads the hiberfile that was created to save the computer state. The computer returns to the last state it was in before the computer entered hibernation mode. Hibernate mode reduces start time.
Note that when you service the computer, make sure you shut down the computer instead of using hibernate mode.
Windows XP supports Hibernate capabilities (ACPI S4 sleep state). Windows XP S4OS Hibernate is available on new computers and upgrades that meet the requirements for the correct video drivers and no VXD audio drivers.
S4 is the hibernation state. It is very close to the APM Suspend to Disk state.
Computer must support APM 1.2, or ACPI.
A paging device that supports D3 (note - certain SCSI configurations do not support this).
No legacy capture devices connected.
WebTV for Windows is not installed.
Non-ICS Host (client is OK).