Unfortunately, Digital Photo Professional was not designed to allow for movie playback. Instead, you need to find the files on your memory card and play them through your operating system's default program (likely Windows Media Player, Quicktime, or another media player). Depending on your card and card reader's speed (or camera's USB connection), the throughput may not be fast enough for smooth video playback. You should probably transfer them from the memory card to your computer first, for optimal playback.