Thanks, I did as you suggested and had some "results" - but not what i expected. So I had a look at my setup further - and this is what I found.
I have a library of .gen .smd and .bin Megadrive games.
The ROM's work in Open Emu and Retroarch on my MacBook Pro. They also all work on PC in Retroarch and standalone medafen emulators - where I launch thru launchbox.
None of my .gen files work in recalbox.
Most of my .smd files work in recalbox.
Some of my .bin files work in recalbox.
So I am - slightly confused, but glad of the feedback as I has made me look at my data.
sTeVE
