The point being made was that there is a technical difference in the two formats that was causing your solution not to work. Telling him to just click on it is completely missing the point that he was having issues with that. He did his homework and found out there was a difference between the two, and was pointing out the technical differentiation between the working and the non working.
You allude, with the legal comment, that this might possibly be warez. Since this worked previously for him, if it was indeed warez he would realize that simply making an image of a movie DVD does not mean it will work since there are such measures as block encryption, block shifting, and combinations of other techniques that would, in most cases, result in a useless image without help from tools like daemon tools.
The the original poster, good job! You would be truly surprised at how *few* people take the time to acertain what the issue actually is, and *rarely* go to the low level you took it to. Please continue to work that way!