Now, the only thing missing from the OP is which OS is the Poser installation.  Vista and Windows 7 will prevent direct access to Program Files folder as a security measure.  Much of the information provided is still rather unclear or too convoluted to exactly determine what is actually happening.  Acadia provided a detailed step-by-step illustration for V4 installation which is, by far, as accurate as anyone could ask for. 

Also, I would advise anyone installing any type of software application, read each step of the installation process.  This is not to be a no-brainer procedure, there are too many hidden steps which will elude you if you choose to rush the installation.  WandW's comment is a perfect example.