Enhanced USB host controllers on Win2K

I noticed that on a machine that has both enhanced USB controllers and
universal USB controllers, PnP Manager will request the user to restart the
machine if the user disables the enhanced host controller and then enables
it while a device is plugged and started on any of the universal host
Can someone explain this situation ?

I remember reading somewhere that the enhanced USB host controller is a
device that is created to support USB 2.0, when this device is disabled all
the USB ports on my computer are still functional, is this device loaded for
a specific hardware ?
I also noticed that the universal host controllers are in the removal and
ejection relations for the enhanced host controller.

On WinXP the PnP Manager deals well with the enabling and disabling of any
USB host controller, the problem only occurs on Win2K (SP4).