make sure you have SR3 installed.

to add a runtime in P7 , you must select the actual 'Runtime'

for instance , if you have a 'Characters' runtime , find it in the browse window, and click on the containing folder (ie Characters) then select 'Runtime' and accept it.

Poser will then recognise the library as "Characters"

 

typical pathing >>>  " F:/Characters/Runtime/.................

 

always choose 'Runtime' as the folder to add, Poser will recognise the library and name it accordingly