I've had bad luck with ACPI myself so I usually turn it off. Usually it needs drivers that support it and a BIOS that also supports it. But drivers and BIOS upgrades can be buggy themselves and be the cause of some crashes.

But here is what Microsoft says about APM/ACPI in Windows XP:
[link|http://support.microsoft.com/?kbid=307525|http://support.micro....com/?kbid=307525]

ACPI troubleshooting on previous Windows systems:
[link|http://is-it-true.org/nt/nt2000/atips/atips58.shtml|http://is-it-true.or...ips/atips58.shtml]

Hope that helps you somewhat.