I just posted this message in another topic:
This is being discussed on the Adobe forum as well…
Someone on there is running an AMD 64-bit processor at 32-bits and it works fine. Right now, I doubt that PPro supports 64-bit processors in 64-bit mode. I’ve heard that even Windows XP Professional cannot handle 64-bit and that there is a copy you can get “somewhere” that probably isn’t 100% legal that can do 64-bit, but even then, unless the software application can do 64-bit, it will not work. I’ve also read reports of even MS Word not functioning on a 64-bit running system, so this is a major issue. I would wait until the end of this year or sometime next year when the “Longhorn” beta versions are released and tested before going with a 64-bit and running it in full 64-bit mode.