Hey, BTW I also have a MOTU interface (slightly different from yours. Mine is an 8 port MIDI Express that works with both MAC and PC) and I had no luck trying to make it work with Windows XP.
Even though I have downloaded and installed the right drivers I could not get my PC to communicate with the Interface. I have tried using different ports and different tricks but it was pointless. Nothing worked.

That is why you can see so much used pre-USB MIDI interfaces going for two bucks a dozen. (I better be wrong! LOL)
Odds are half that stuff will not work with XP and even OSX.

-ED-