Have you tried extracting to a dummy folder aand checking the folder structure? Sometimes it doesn't start with runetime so when you extract straight into Poser you will have to look for it. As far as p5 vs p7, the materials may or may not work properly. The readme did show where the files were placed. As Bar-Code mentioned, check the readme then see if the files are where it said they should be.

I must remember to remember what it was I had to remember.