I've worked with 3D for 5 years but I'm new to Poser5. It may seem obvious to most of you but this was exactly the question I wanted to ask. Looking at tutorials and discussions I find plenty of references to "multiple runtimes" but they assume you have already experienced a runtime and understand what goes in it, how it's organized, how poser finds it, etc.... 

2 questions:

I guess Poser needs a runtime folder, but it bloats when everything is in there. So you create an external runtime and navigate within poser to get to the external folders. (correct me if I'm wrong) Then the PZ3 just references all the external files without saving the geometry/textures/etc within the PZ3? If you re-organize the external runtime folders your PZ3 can't find the files and you will have to re-locate them?

Does anything HAVE to be in the default runtime? If so, what? Would it make sense to back-up a runtime for every important scene? In other words, if I want to back-up my scene (like to CD-rom) should I make a runtime that contains everything in that scene? That way I can go back to the scene or character and know I have all the parts?

thanks for helping a noob.
holly