Well I have installed since the beginning everything on the default folders, I di have several drives both internal and external but the other drives I only use to download the files from the websites, after that I only installed to the default recommended location. This what the vendor wrote to me.

" Have You reccently upgraded to a new version of poser? Like poser8 or poserpro2010? And if so, are you using external Runtimes (runtimes that are not located inside the new version of poser)?  I still think it sounds as if poser can't find the right files. You can try and install again (just overwrite the old install). If you have a new version of poser install into that runtime. Is thorn working in earlier versions of Poser? (If you have any earlier versions). If he don't, your download might be corrupt. It's unlikely but not impossible.
That's all I can think of right now.