Saving to .iso in DVD Shrink

I have DVD Shrink installed on 2 computers. On one, when I backup a set of files to .iso, I get an .iso, however, if I do the same thing on the other computer, the output when I select backup to .iso is a set of files including a .mds, .i01, i02....

Can anyone explain this? I prefer the .iso as I can save my movies as a single file and play easily with VLC. I know there must be a setting causing this but I have tried everything I can and it stays the same.