If you're running Windows, then the only thing that will change is that P6 will be associated with PZ3 files for opening when you double click. There are no other changes in the registry that I've been able to find (no entries period, other than file associations). The above is almost certainly correct information. Apart from one obscure registry key (which I think was concerned with the activation security in early versions of Poser 5), somewhat surprisingly the only registry keys that get added during installation of Poser 5, are merely file association keys. From the comments above, it would appear that Poser 6 follows a similar pattern of installation.