The Pro version of Mover 4 has the support for Python scripting and the wind effected plants for the RenderCow system. A couple of people I know tried to use their existing Vue Cow setup with Pro....and found it did Bad Things, at least whenever the managed to get more than a CTD or BSOD (The two apps Cows do co-exist very nicely on the same renderboxes, though..at least as long as they are on different ports. They just are not cross compatible). It's the same with the Mover 4 add-on version that comes with Pro; standard Mover 4 isn't compatible with VuePro; even if you somehow managed to beat VuePro into loading it, all it will do is break the install. Badly (I had a bad install, and just for fun I copied the relevant Mover 4 files out of Vue 4 into Pro. Boooooom....) The Mover add-on is -mostly- just a Poser plugin, but there is some additional animation support features added; 'Mover' is the actual name of the basic animation system that is native to the Vue 4VuePro line. That's why the add on appeared as 'Mover 4', not just 'Mover'. The Mover 5 package may have been coded so that it -does- intstall to either package, and has dual code tracks so that the installer loads the correct version. Does that make any sense?