I'm assuming you're using Windows.
Actually, you CAN make a video of a powerpoint. This is my method:
Use a video capture program (If you don't want to spend money, try CamStudio) to capture a video of your full screen, while you operate the presentation. In your capture program, make sure your mouse isn't visible when recording.
Save the file as an .avi, and use Windows Movie Maker to shrink the video so it can upload into Youtube with minimal quality loss.
Use Windows Movie Maker to cut off the parts where you start and end the presentation, and use it to add sound if necessary.
Remember, you can use other video programs if you want. My example is for Windows only, Mac users will have to find a video screen capture program for Mac, and instead of Windows Movie Maker use iMovie.
After you've edited your movie, save it as a movie file (WMV) and upload it to Youtube.
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