If you press ‘i’ on your keyboard to show player status window, are there any errors displayed there? (when the screen is black it suppose to player .ppt layout)
You can also see if the presentation file is downloaded (under required files on status screen).
Alternatively look in schedule.xml and requiredFiles.xml files (in your player library)
Am I right to assume that there is no other items on the layout and no background image? Just the ppt module?
While we do recommend saving presentation as videos, .ppt original files should work on windows clients as well - assuming that PC running the client also have PowerPoint installed of course.
Basically with the module enabled and PP enabled on display and installed on the PC, it should make at least an attempt to open the file - the registry entries and PowerPoint media items show a "Navigation Cancelled" error when running on the Windows Player / PowerPoint brings up an Open Dialog are just to prevent the dialogue window being opened up each time)