ACPI Extensions (Acpikd.dll and Kdexts.dll)
Extension commands that are useful for debugging ACPI (Advanced Configuration and Power Interface) BIOS code can be found in Acpikd.dll and Kdexts.dll.
Some of the ACPI debugging extensions can be found in Winxp\Acpikd.dll, while others can be found in Winxp\Kdexts.dll.