Vista and Window 7 have virtual folders which files are relocated to when attempting to save into the root Program Files.  I do not have my W7 computer running at this moment so I cannot give you an absolute path.  But this topic has been covered in other posts before.  There are 2 workarounds within these OS's, either disable UAC if you haven't given proper authorizations or install your Poser app to the root directory as whbos mentioned.