In Windows 2000, PCI devices share IRQs, specially on APCI computers.
IRQ9 is normally used.
Windows 2000 does not have the capability to rebalance these resources. This is the result of the Plug and Play implementation used by Windows 2000.
On a non-APCI computer, you might be able to manually set IRQs.
If you need to set IRQs on an APCI computer, you must disable APCI in the BIOS, prior to installing Windows 2000.