The ONLY way to disable ACPI support in Win2k is to disable it in the bios BEFORE installing Win2k. You cannot disable it after install, win2k is unable to adapt to a system change like that.
There is a little more to ACPI than meets the eye though... First of all, all your devices are not really sharing irq 11 (or 9 ) the system only reports that. ACPI allows the system to dynamically steer IRQs around as needed at the time. The benefit of this is that you don't run out of IRQs so quickly. The downside is that drivers can be very tricky to get that work correctly with ACPI enabled. (My win2k sp2 system is using ACPI, no problems at all.)
It looks to me like you have a Radeon card in your system though. ATI still can't write a quality driver for Win2k, let alone one that works right with ACPI on.
Here's what I would recommend. Load all the newest drivers and leave ACPI on see how things work. If the system is not acceptable, burn all those new drivers, sp2, AMD large page file registry patch, via 4 in 1 4.29s (or 4.31s), Direct X 8a, and anything else you don't want to download again. Format the hard drive

. Turn off ACPI in the bios, leave plug and pray on. Install Win2k, install via 4 in 1s, install AMD registry patch (large page update), install sp2 (it includes fixes in SP1 as well, but you are going to need the big 100+ MB full .exe file, not the express install), install video drivers, install all other drivers, plug the usb stuff back in and install their drivers, write a nasty e-mail to Bill Gates for making this such a pain.

I'd also be a little worried about installing Win2k with the radeon card in, but if it doesn't work just pop in another card to do the install, then put the radeon back in.
As for AGP 2x or 4x, I wouldn't worry about this too much. The speed difference is minimal at best.
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bloom25
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THUNDERBIRDS