Unzipping and zipping .crtx files

[SteveG]

I have created some customised chart templates that are saved as .crtx
files.

When I unzip these files I see a whole bunch of xml files, folders
and ... in a folder 'media' I see the thumbnail image1.bmp that is
displayed in XLS. I though this might be a way I could make my
customised charts stand out so I have tried to substitute a new
image1.bmp.

I then rezipped all the files and folders and changed the extension
back to .crtx

Unfortunately I must have done something wrong as when I go back to
the 'My Templates' window the .crtx file and the thumbnail is
missing.

Is there a file containing a list of .crtx files somewhere else that
is used to determine what is shown?

Steve
XP & XLS'07