Problems with .iso files

Since this is my first time at this forum and i cant find the correct location to post my problem in, i will do it over here.

I have download a movie, wich has been resulting in to two files on my computer. One is a .iso and the other a .dms. I want to watch this movie on my MacBook Pro. Tried to mount the .iso file and start up the dvd-player, but it's keep telling me the same stuff. It's doesnt seem to know the file partition.

I looked further on the web and tried also VLC Media player, but that has the exact same problem. It seems that 'm doing something wrong, can anybody tell me how to watch this movie?

Looking forward to your replies