Attached Link: The Poser File Disposition Guide, Part 1

A pz3 is a Poser document or "scene" file. A pz2 is a pose file. A pp2 is a prop file. A cr2 is a character file. All except pz3 must be placed in the correct path within the poser library. I don't think nruddock's sugestion will quite work, because a pz2 can't load a prop, but the idea will work if you use a pp2 file extension. Editing down a pz3 so that it only contains the lights and shadow cams, then saving it as a pp2, is probably the most elegant and professional way, but it is also a lot of work. Here is an easy way to achive what you want. Download and install my 'MinFig' from the Free Stuff. With your light set loaded in Poser load MinFig. Parent "MainLight" to MinFig. Save MinFig back to a Figures pallet with a new name (say "MyLights-001" for instance). Props lights and cameras parented to a figure will save and reload with it. Because in your case everything is parented to, or part of a parenting chain that leads to MainLight, if you parent MainLight to MinFig, then save it all the children will save with it. For more info on where Poser files go see the link above.