Putting video inside your online course can enhance learning if it is done well. That's a big IF, but still, good videos are useful ... as long as you can see and hear them. Unless your college has a dedicated multimedia streaming server, you should look at alternatives rather than uploading your video files directly into D2L.
This video above promotes embedding videos inside a Desire2Learn online course by using the free video hosting services such as YouTube and Blip.tv where they will convert your video to flash and give you the html embed code for you to paste into your D2L course. Easy, peasy.
Direct link to Blip where there is a full-screen viewing option.