Unload external swfs problem

I’m having a problem with a tutorial I found here at Kirupa.com.
The problem is that I want to unload/remove a swf or jpg I’ve loaded when I press another button in the main swf. The reason why I want to do this is because if I click on a button which I’ve linkaged with a movieclip in the library the external swf or jpg is still visible in the background.
I’ve tried with unloadMovieClip (transition and content) various times but it wont unload the previous loaded swf or jpg. Maybe I just can’t find the correct path to where the swf or jpg loads.
I guess that there’s no “remove every loaded externals” script, so what should I do?

Almost forgot, link to the tutorial http://www.kirupa.com/developer/mx/preloader_transition.htm

/Erik