I know that the Desmume does not have an 'official' save function and that you must rely on save states. (Unless I'm wrong, I've tried the methods in the faq such as extracting it to my desktop) However for 999 every time I finish an ending it saves itself and deletes the ending I just received. Now for the most part I wouldn't have a problem with this except I need one of the endings to unlock the true ending.