Does the DVD play like on a normal DVD player? Trying to find out if you have a real DVD formatted video.
If you just copied off the data, that is not how to take a DVD to a computer. It has to be converted off.
You said it is a personal video he made so if that is the case, look up Handbrake on Google as it can convert it for you. Even has setting for iPhone.
Use the DVD he gave you as I don't know what is up with that DAT file.