This is a similar problem to yours:
http://www.chron.com/cs/CDA/story.hts/tech/weekly/1439314
"Configuring Advanced Power Management
Windows XP Professional supports Advanced Power Management (APM), which helps reduce the power consumption of your system. To configure your computer to use APM, use the Power Options Properties dialog box. Click the APM tab and select the Enable Advanced Power Management Support check box. If the APM tab is unavailable, your computer is compliant with Advanced Configuration and Power Interface (ACPI), which automatically enables Advanced Power Management Support and disables the APM tab. You must be logged on as a member of the Administrators group to configure APM.
If your computer does not have an APM BIOS installed, Windows XP Professional does not install APM, so there will not be an APM tab in the Power Options Properties dialog box. However, your computer can still function as an ACPI computer if it has an ACPI-based BIOS, which takes over system configuration and power management from the Plug and Play BIOS."