If you are referring to Generation 4 morph packages from DAZ for V4, M4, etc, those should always be installed into the runtime containing the base models and initialized.  It doesn't matter where the runtime is externally located.  As WandW posted, do not install into Program Files for those OS mentioned, always install into external runtimes or the Poser Content folder which, by default, should be located in a separate share folder.  PMD's are always located on the same level as the cr2's, within the same folder.  It doesn't matter whether it is on or off in the General Preferences, Poser will still recognize it.  However, if you have multiple instances of the same file linked to the Poser Library, the pmd's might not work correctly, even though I haven't seen this happen yet.