I'm running Win XP Pro x64 (quad) and Poser Pro. I have found the best results rendering a series (or multiple series -- to reduce task sizes) of images to be the most effective.  Using Pro, I send the animation to the render queue, usually in blocks of around 10 seconds (300 frames or so). I can then assemble the frames as video clips in a video editing application.  (I render to uncompressed bitmaps.)