Your BIOS experience has to do with the ACPI support in the BIOS (I think that's right). If it's off when you install Windows 2000 - and probably XP - then there's a core component that is different than if ACPI is on when you install Windows 2000. Of course, NT's support for power management and device enumeration is older and can get confused if things aren't what they seem.

Also, Windows likes to control the PC. The BIOS setting "Plug-n-Play OS" is really misnamed. It should be called "Windows OS" because when it's "on" it sets up the device enumeration in a way that Microsoft insisted Windows needs for it to diddle as it likes. This would also contribute to NT behaving oddly.

Now I'm glossing over stuff here, mostly because there are a lot of details I don't know.

Wade.