Maybe it is I not understanding, but if you don't have the original
template, then the discussion is over: you can't edit the template. There is
a common misconception about PowerPoint templates and how they interact with
presentation files: the template governs the initial design but there is not
a link created between the file and the template. (You can always reapply a
template if it changes, but changing a template does not change a
presentation file on which it was initially based).
-- Maybe all you need to do is to get to your slide master: View | Master |
Slide. Perhaps that is what you mean by the "background template"
-- Maybe your background template is an image or photograph that needs to be
changed, and you will need to work on it in an image-editing program.
-- Or maybe you just want to create a new template, which you can do pretty
easily from your presentation: File | Save As | Change type to Design
Template. Then you can easily create other presentations based on this
design.
But the missing design template does not hold a key to the puzzle that you
do not already possess in the presentation file itself.
