Which version of Poser? 7 can cope with M4 and V4 in an external folder, so you just need to tell it to use the Content folder or wherever you installed to as an external Runtime (keep double-clicking the up-a-level icon in the Library panel until you hit the top, with just Poser and Downloads listed if you haven't already added folders) then click the + button at the bottom of the panel and select the folder that holds the Runtime folder with M4/V4 in it. If you don't have SR3 for Poser 7 you will need to set the Search behaviour to shallow in Edit>General preferences. If you have Poser 6 or earlier then you do need to install M4 and V4 (and morph sets) to the Poser folder, unfortunately.