In the interest of other people reading this, I thought I'd add a bit
more...
In the page that the link produces,there are three possible fixes.
The first one using " Re-registering" Powerpoint didn't work...
The next step, right clicking and choosing program to open with,
also didn't work...
The third fix did work,
Editing the Open action for the file association directly...
It's all there in the link provided by Geetesh Bajaj.MVP
Thanks again guys...