Information concerning ACPI may be found here (sorry, all links are broken...):
- Steinberg KnowledgeBase
- Tweak XP
- Microsoft KnowledgeBase
If you are considering disabling ACPI support, please note the following: disabling ACPI on an existing installation may crash your system; consider protecting your valuable data - use a drive image/ghost backup application; any resulting increase in audio performance may be less than expected; ACPI issues typically cause problems only when your soundcard shares an IRQ with other PCI/AGP cards; before disabling ACPI, try moving your soundcard to another slot to see if that helps.