Hi. I can tell you how to load external clips in Flash MX (it will probably be more or less the same in Flash 5).
First, create a movieclip that is as big as the file you want to load.
Now, drag this clip from the library onto the scene.
Call this movieclip dropZone by editing the instance properties.
Now, in the frame where the movie must load, add the following ActionScript:
loadMovie("external_clip.swf",_root.dropZone);
This will load the clip called external_clip.swf into the dropZone area.
If you have any more questions about this, rather e-mail me than replying to this.