In your mame directory, you have several sub directories that contain game specific settings. One of those is 'cfg' which contains the settings for inputs among other things. When you launch a game for the first time (e.g., asteroids), mame will create a file in that directory with the .cfg extension (e.g., asteroids.cfg). If you don't adjust any of the settings for inputs for that game, the file will be mostly empty. In that case, the settings that will be used for inputs will come from the default inputs (stored in default.cfg). If you get everything screwed up and just want to start over, you can always delete the .cfg file for a specific game, the default config, or everything just by deleting the appropriate files in the cfg directory. In this case, you want to start from scratch on Asteroids, so go to the cfg directory and delete asteroids.cfg. If you still have problems, go back to the cfg directory and delete both asteroids.cfg and default.cfg. Be aware that if you do this, you will need to set up your default controls again. Hopefully this description will be enough detail to help. If not, just ask for more specifics and either myself or someone else can fill in what's missing. Good luck!