would be helpful to at least have the model number of the WD Passport, but here is a link for 'Downloads'-My Passport (you just have to choose which model you have, should be listed on the underside of the unit)
We have a WD passport that was given to us as a gift with about 70 movies on it. We use it just to watch movies. It was working fine a few days ago. Today we plugged it into the computer and when you click on a movie it says 'File is not a movie file' and we can't open any of them. Why on earth is it doing this?