After I installed Poser5, I copied the Geometries, Libraries, Reflection Maps, and Textures folders from my Poser4/Pro-Pack Runtime directory to the Poser5 Downloads/Runtime directory. Everything seems to work. A lot of the stock stuff is duplicated, but at least things work and I can access all of my old stuff and the P5 stuff from P5. Someday I'll delete the duplicates.