Newbie question - how play DVD's?

[lmkk]

Just bought my Pi and have installed xbian 1.0 Alpha 4 on it.
And now I have problems playing DVD movie on xbian - I have purchased the mpeg2 and vc1 licenses and added them.
On my nas I have the DVD movie as ISO's where these ISO contains (when mounted) audio and video folders where the video contains x_1.vob and x_2.vob.
If I press "select" on one of the vob it plays that part/section of the movie fine, but I can not get xbian/xbmc to play the whole movie in go (I hope I making sense).
How do I solve this? I have tried pressing play both on the root folder of the movie, and the video_ts.vob with no success. Can anyone help out?