To the last point: Macs have a data (resource) fork, and a program fork. Both are stored within the single program file. (This is where resedit - Resource Editor - comes in.) Windows unfortuantely had no such concept back when Poser was first ported to the PC. So the solution that CL, or more correctly Metacreations, or even Fractal Designs (?), took when porting was to create a separate file on the PC to house the rsr part. This is a disaster-waiting-to-happen solution, 'cos 2 files to be updated synchronously spells point of failure in a crash. (One gets written/updated, one doesn't.) Fortunately later versions of Poser have removed the dependence on all .rsr files bar the poser.rsr one, as indicated above. Presumably when Poser 5+something gets written the switch to XML configuration started in PPP and extended considerably in P5 will be completed, and result in the dropping of this last "rsr" file.