I had my new Athlon 64 X2 4600 box shipped with Windows x64; I've been running on it for over six months now with no problems. Since all of the components are from larger manufactuers, I haven't had any driver issues...I've found that on the whole, I haven't reallly noticed anything different from Windows XP (which, I suppose, is actually a good thing). Poser 6 behaves (as well as it ever does, I guess), but I think until they rewrite the program for 64 bits that there will be much of an advantage over running it on Windows XP.