The "install" button just downloads them. You need to copy them to the correct directory in order to "install" them. The thing about PND files is you don't actually install them. By simply putting them in the appropriate directory (depending on whether you want it on the desktop or in the menu) it'll just appear there. You can then delete the PND file later and it is just gone. Save games and profiles are kept, however, so you can easily download the PND file again and just copy it back and everything is as it was. MAGIC!