I am not a very experienced Poser-user yet, but from my experience I can say that it is always best to re-install everything inside PG's main folder. Personally, I started with P5 default with SP4.1 without the content room. I set Poser to open with no character on the scene and deleted everything from the runtime folder that I wasn't going to use. In my case, only Don was kept. Then I installed the meshes I bought at Daz and installed the various characters etc I bought here. I know it is a lot of work, but imo the only way to be shure everything is ok. Second best solution is to grab your P4 runtime folder in explorer and copy it to your P5 folder.

I have tried prudent planning long enough. From now I'll be mad. (Rumi)