A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
When you add an image / shape to a master or layout then under the hood in the XML PPT marks that shape as 'userDrawn= "1" '
In many circumstances when you apply a new template this is interpreted as "They drew it so they must want to keepit!" This is why you can get duplicates. Also because there may now be layouts with the same name that differ it can create "layout_1" files.
There's no way to turn this off in the GUI you would have to edit the XML in a good XML editor to remove userDrawn=1 or set it to 0.
If you are a bit daring we have a prototype app to kill the userDrawn attribute in potx files but it was only meant for in house use and isn't bug free and doesn't have a proper GUI! If you want to give it a shot email me john ATSIGNpptalchemy.co.uk. If you just need evidence it works send me a potx that duplicates logos and I will run the app on it for you to check out