Right, copy your files that have everything in that you want to keep. Paste them in your documents. Delete the Feral Heart folder and empty your recycle bin (if you have one). Delete the installer too. Delete the old patch installer. You still have the files you wanted to keep in your documents right? Then re-download the installer using the download option (or torrent, the torrent seemed to work better for me but only for the game itself, not the patch). Make sure anything else feral heart related is deleted from your local disc C: drive, even the short cuts on your desktop or task bar (if you have windows 7) other than feral heart plus if you have it. Once you're sure everything is deleted and you've emptied the recycle bin and downloaded the installer for the game, run the installer and install the game again. Do not add your old files yet. Get the new fh patch (optional at the moment as the patch and server are having issues) installer and install that later.
This should work. It worked for me earlier.
Add your old files once you're sure the game is working but don't over do it, like, add 356 meshes to it or something for map making and so on. You can add more stuff to it gradually when you're sure it works.