USB versus PS2 Keyboard

[Mervi]

Have a user that need to be able to use both a PS2
Keyboard and a USB keyboard (have an ergonomic keyboard
where the keypart can be split from the numeric part, and
the numeric part is the most important) connected to the
computer at the same time. OS is Win XP Pro.
Can use both keyboards if starts with only PS2 keyboard,
then after startup connects the USB keyboard. If they need
to restart for some reason, the PS2 keyboard does not
respond after restart.
Is this by design in Win XP or is there a workaround? Any
suggestions welcome!