I'm not sure if mame is preconfigured with key assignments for player 3 & 4,I know for sure that player 2 buttons 5,6,7,8 needs to be assigned keys before they will work in mame.Just open up windows notepad and hit the buttons that are not working,if they spit out the keys you programed into the ipac for those buttons then you know the ipacs working and you need to configure your key assignments in mame(hit the "tab" button while a game is running to pull up the mame options menu)just be careful which submenu you use,there is one for all mame games,and one for the particular game you were playing when you opened the options menu.One effects all games and the other only effects the active game you are playing.