First follow LIGHTNING UK!'s advice.
You need to install Virtual CloneDrive & mount an .iso that works in one or both of your players.
If you already have a virtual drive you can probably use that.
Nero Info Tool can give some information about the .iso after you get it mounted.
The Dune HD media player is a hardware player so it may not play the same .iso file that the J River media player a software player does. I suspect the J River media player will play more of your .iso's . It's my understanding that at one time it came with virtual clonedrive & still may. I don't have it so I don't know. It automatically mounted the .iso in virtual clonedrive & played it from there.