The problem is in your command line. Running: cmd.exe /c C: C:\Emulators\MAME\mame.exe 005 -rompath C:\Emulators\MAME\roms -nowindow -joy -skip_gameinfo -bezel -artwork_directory artworkgameex And just for argument's sake, the next entry is different for some reason: Running: cmd.exe /c C: mame.exe 005 -rompath "C:\Roms\MAME\Roms" I would start by making sure your MAME path is correct, and maybe post your MAME INI so we can have a look at that too. It definitely shouldn't be doing that. GameEx doesn't switch command lines for me like that... Something screwy here for sure.