Also, I would advise not listening to "gamez fan", he's trying to confuse you by suggesting you download another MAME ROM set when Galaga itself actually works just fine. He doesn't seem to understand that when you're already confused about how to run MAME, telling you to go and get some other game doesn't really help you at all.
Thanks for that but i was just mentioning to the guy there was other options in order to be able to play galaga in MAME plus with Namco Classic Collection Vol 1 he had the bonus of the galaga arrangement version also.