MGD sets are different and no amount of romcenter work will fix them. The real NRX (last version 0.6c) supports this format, but the hacks do not. The really bad thing about MGD's are that quite a few are bad dumps! You would be better off playing those early neogeo games on kawaks, mame, or nebula (and using mame romsets). For those used to reading MAME code, here is the weird code needed to get an MGD set working: As you can see, bytes need swapping about, and entire blocks are in the wrong places.