Ok, here is my Powerpoint to Isadora solution. Its a few years old now and I added a few lines in the VBA script today, to correct some instances that may appear when people are creating PowerPoints that interfere with a smooth transition. Please follow the guide I have added. There are also two PowerPoint examples you can use to test. Unfortunately you don't get around to convert the file to UTF-8 because I couldn't find a way to tell Powerpoint to do so. Its all explained in the guide.
To go back and forth in the presentation press the left and right arrow keys, or klick the spacebar to go forward. To scroll forward quickly klick into the current slide number and scroll up or down with the mouse. You can also type a slide number into that field to directly jump to a slide.
Best Michel