I am running Vista Ultimate on x86 and have had no problems. I installed the old, old version of PMM that came with my keg software. At that time it couldn't install the AT&T voices. This wasn't a big deal as I had purchased the nicer ones (they are worth it). I installed the new AT&T voices, PMM 3.92 and that was it. I had to assign admin priveleges to the PMM .exe file but I've been cruising along since (had to give Yamp admin priveleges as well).