If the content has more than one character fit then just create a runtime for that specific content (i.e., Hair).  Everything will be contained within and easily accessible.  Installing into each character setup is waste of computer space and resources.  Judging from the title of the thread, you are running PoserPro (please there is no such a thing as Poser Pro 7; it is either PoserPro or Poser 7), there is a collection tab in your Library palette to further organize your content.  You can link content from external runtimes into centralized folders for easy access.