thats an image file, you need to burn it to disk with something like dvddecrypter or nero etc
I'd have bet £50 Mofo was responsible for this thread but I'm shocked..
Install daemon tools, right click the icon in the taskbar and mount the image - runs just like a cd then
The latest versions of Daemon tools has spyware in it so I was told by a colleague... Don't know if it is true or not but I am using Slysoft Virtual Clone Drive these days. Its free and works perfectly, and yes, you use it to "mount" DVD/ CD image files without having to burn them first.