Bluetooth Keyboard on XP and Vista together

Hello,

My Computer:
AMD Athlon 64 3000+
Asus Board with VIA Chipset
A Microsoft Intelli Blutooth Keyboard/Mouse Bundle with Microsoft
USB/Bluetooth Stick

I have on my PC a working Windows XP, now I added on a second partition the
new Beta 2 of Vista. The Bluetooth mouse works in both systems, i think
because it has no Bluetooth key. The keyboard on the other hand, if I start
the other system, I allways have to delete from Bluetoothdevicelist and
reregister. I already tried to register on both Systems with same Key but it
didn't work.

My Question is, how can I make the keyboard work on each without
reregistering after each switch.

thanks