Never mind ... I now know I can set up PPT templates in InDesign. Just have never used the program for that purpose. I almost got a freelance job doing this, but it fell through.
You can set up a PowerPoint template design in any design programme. I'd be most surprised if you can create a working PowerPoint template in anything except PowerPoint itself. There are quite marked differences between versions, for one thing.
Also, designing slides in Photoshop is non-optimal, to say the least.
Yes, WW, that's what the client was asking for (it was a bit unclear) new templates for PP slides to be done in ID. His files were in a version of ID I couldn't open anyway. Oh well.
^ I do a lot of template work for design companies that create in InDesign. I don't even have InDesign myself, but a PDF is a more than adequate substitute.