Hi,
Strange. when you say they don't load, what happens when you click on a piano type? Other than nothing of course! Go to options on the interface, at the very bottom of the screen that comes up you will see the 'path to library'. Make sure that is pointing to the place you installed the .nki parts in. When you have done that, remove the plugin and select it again. Let me know how you get on. Also, check that your puter is actually seeing your external drive. Again, it may sound obvious but these things have to be checked!