I have the latest BIOS version (2 November 1999) for my Chaintech 5AGM2 board and I still can't use APM in Windows XP. If I try to enable it via the Power Options in the Control Panel, I get a stop-error on shut-down or restart that disappears too quickly for me to see (I've turned off the option in Windows XP to 'automatically restart' when stop-errors occur, but this stop-error still disappears).
Funny that the new BIOS update now includes ACPI in the Power Management options of the BIOS, even though Windows XP installs APM.
I don't understand what's going on or why. I can still have my monitor and hard drives power off though. Sounds like having APM enabled is a luxury I can't have.