Can't find audio track

Hi Brains trust.

This one is doing my head in.

I have created a new SL project and copied a single slide from a large existing SL project.  The single slide only has a few images on it with no triggers or layers and there are no multimedia files in the timeline.  See attached.

The thing is that the new project seems to now contain all the multimedia files from the original.  How do I know?  The file size of the new project is 200mb+ 

Is there a way to locate the multimedia files so that I can delete them? 

Thanks in advance.