1. The article [Q314088] describes the process used by Windows to enable and install Advanced Configuration and Power Interface (ACPI) functionality. An ACPI system consists of a series of 10 tables that define which devices are present on the system and what their capabilities are as to configuration and power management that are built by the system BIOS at startup. When the computer starts, the system BIOS looks for specific entries in two of these tables, 1) the Fixed ACPI Description table [FACP] and 2) the Root System Description table [RSDT] to determine whether the system is ACPI-compliant. Information is extracted from these tables in the form of an OEM ID, OEM TABLE ID, OEM REVISION and CREATOR REVISION. If these tables are not present or if the information in those four descriptors is invalid, the system is assumed not to be ACPI-compliant and the legacy hardware abstraction layer (HAL) is installed.

2. In order to use the ACPI Power Management features in Windows XP, a computer must have a compatible ACPI-compliant BIOS and if it does, an ACPI Hardware Abstraction Layer (HAL) is installed which allows the use of ACPI power management features. If the computer does not have an ACPI-compliant BIOS, a non-ACPI HAL is installed and ACPI power management features are not available.

3. Note what the article [Q306458] states.