I would update Win 2000 to the latest drivers and service pack but I would definatley keep Win 2000. The choice is up to you, but I know most editors prefer Win 2000.
Enjoy your RTX10 I'm sure you'll enjoy this card.
On the other hand, more camcorders work with XP, which has "the" latest firewire support. In fact, Matrox tests the RT.X hardware with XP, not 2000. I'm running a dual Athlon with my X100, and it will only run on XP and won't run on 2000 reliably at all.