The first thing to check is that your hardware can play the DVD you have used to burn the film on.
ie: If it is a DVD+RW some will not play that.
The second thing to check insofar as relates to the computer, as against the DVD player, although the same principal regarding the type of DVD applies to that as well, is that you have the right codecs installed to play that DVD.
What are you using to play it - ie WMP or some other program.
Having assured yourself it is the CORRECT type of DVD write. If it is a matter of WMP and codecs you would receive a message to that effect.
If it is an issue with WMP TRY this. It is free and will play many formats that WMP rejects
http://www.videolan.org/