Have you disabled ACPI in BIOS?
"The Plug and Play operating system settings in the computer's BIOS should not affect how Windows 2000 handles the hardware in general. However, Microsoft recommends that you set this setting to "No" or "Disabled" in the computer's BIOS. For information about viewing or modifying your computer's BIOS settings, consult your computer's documentation or manufacturer. Manually assigning IRQs to PCI slots as a troubleshooting method may work on a non-ACPI system, but these settings are ignored by Plug and Play in Windows 2000 if ACPI support is enabled. If you need to manually assign IRQ addresses to a device on an ACPI motherboard, disable ACPI in the computer's BIOS before installing Windows 2000".
To force ACPI Win2K not to install ACPI, when installing, see
here