Instructions on Opening PowerPoint with JAWS from A File on a Disk, Machine or Floppy Drive
PowerPoint by itself is inaccessible to JAWS but if opened through Internet Explorer, JAWS will read the text. JAWS will not be able to read or otherwise identify an image.

Open JAWS, and then open Internet Explorer.

Go to the File menu in Internet Explorer, select Open. In the Open box that appears, select the Browse button, and navigate to the PowerPoint file you wish to open. You will probably have to change the Files of type: to All Files instead of HTML files.

Once you have the file open in Internet Explorer, go to the Edit menu and select Edit Slides. What should appear at this point is the PowerPoint presentation in the Internet Explorer shell; the presentation will be on the right-hand frame and the thumbnail and Outline view will be on the left-hand frame.

Select the Outline view. Use the JAWS reading keystrokes to read the text.