I run a dual boot system with XP Professional in one partition and XP x64 edition on the secondary one. I installed Vue6 in both partition and run some sample scenes just to check that everything run fine, no problem detected, but no significative performance gain of the 64bit op.sys Vs the 32bit. I believe it could only be handy when large size rendering are required or with very complex scenes. Both Vue6 install was activated without problem.