The information contained in the RSR file is integrated into the main file on the MAC (like the thumbnail image and the info on what program created the file). MAConverter will combine the PC files into one and set the file type (creator) so you don't have to do it manually in ResEdit (among other things). The biggest advantage is that you can convert your MAC file to a PC file to share with others. It is a simple matter to re-convert back to MAC. I havn't found any poser file that wouldn't work after using MAConverter.