The biggest huddle many users encountered with the latest iteration of Poser and Vista/Win7/Win8 is the installation options Poser provides.  Unlike WinXP, where content downloads could be placed in Poser's core runtime within the OS's Program Files folder, the latest Windows OS write protect any files within aforementioned folder.  This means any content installed there will be denied full access.  P8, PP2010, P9 and PP2012 will give you the option, upon installation, to separately create a content runtime in a share folder under Documents, away from Windows secured areas.  Also, by selecting this option, the newly created external runtime is automatically linked to the Poser Library. 

In your situation, if you haven't gotten ahead of yourself reinstalling content, you can reinstall Poser again and select the correct option to address the external runtime, or create individual categorized external runtimes and manually link them to Poser.

Now, IIRC, V4 and M4 installers will search for the Poser.exe file unless you manage to obtain zipped format files from DAZ.  (I honestly don't know if they have fully converted their PC installers to zips yet.  If the installers insist to be installed into the Program Files folder, you can offset the problem by placing a dummy Poser.exe into the folder containing the external runtime, not the runtime itself.  By doing this, you force the DAZ installers to prompt you for an installation path which you redirect from Program Files to the folder of your choice.