If you've got the IFO files as well (which you should have if it's a straight rip) then you don't need to add the VOB extension as mediaportal comes pre-configured with IFO and will pick them up, but as FlipGer said they need to be in the VIDEO_TS folder to work.If it's in folders (i.e. .vob files), then you need to add the vob file extension to your movie settings.
I have my vobs in a seperate folder
In My Movies I see the Cover from the Movie. When I click on it I can see each VOB file. How can I do it to play the Movie when I click on the cover?
Yes. Now I habe the video_ts folder and it works. Only at one movie I have a blacvk screen