MAME cannot locate the CHD file. Fix: Ensure the CHD is inside a folder named exactly as the ROM (e.g., roms/mvsc2/mvsc2.chd ). Also, check that the CHD is not corrupted—redownload if needed.

Your PC may not support full NAOMI emulation, or you are using software rendering. Fix: In mame.ini , change video from auto to opengl or bgfx . Disable "Threaded Rendering" if you experience stutter.

Because these discs contained massive amounts of data (often nearly a gigabyte), they cannot be stored in standard ZIP files like older ROMs. Instead, MAME uses the format.