What I recommend you do is to go and download a free app called 'HandBrake' at the following URL http://handbrake.fr/
Here is a copy of some info from the site.
What HandBrake Is, What HandBrake Isn't
HandBrake is a GPL-licensed, multiplatform, multithreaded video transcoder.
HandBrake is not a ripper. It converts video, it does not rip it byte by byte. It does not crack the latest DVD copy protection schemes hatched by the studios.
It converts video from nearly any format to a handful of modern ones—that's it.
Check it out and let me know if you don't come right.