I wouldn't recommend it unless you can separate the content from everything else.  However, this is the bottomline, when installing Poser P8, P0, PP2010, PP2012 on Vista or Win 7 you will be prompted where to install your content.  Old time traditionalists will install content into the main Poser runtime, that is one of the options.  But, if you bother to read the other options, one will recommend installing the main program in Vista's/Win 7's Program Files folder and the content into documents/my documents.  You can also create other external runtimes in that same location and link them to the Poser Library.  This arrangement offsets UAC interference and allow content to be viewed as in earlier versions.  If you are inclined to uninstall, then reinstall Poser as per it's recommended option, you will correct the problem and see everything in the Library. 

Unless you are really sure where all your files are located under the present installation, relocating them will eventually break Poser to the extent that you will be forced to uninstall/reinstall as a final solution.

 

Edit: Old files will still work but if they have associated texture files, you might get missing files errors.