MAME

MAME stands for Multiple Arcade Machine Emulator. Its purpose is to document the inner workings of those pioneering games of the video arcade era. Remember Pacman, Space Invaders, DigDug, etc, well, they are all documented and what's more fully playable in the MAME project. MAME is software, written in 'C' and 'ASM', which emulates the hardware of the original machine the games were built with. This enables the original game programs (often called ROM images) to run quite happily on a PC. The other advantage is that these games will be preserved forever, thanks to this project.
You can find out more about MAME, download a copy as well as many of your favourite games from the past, from http://www.mameworld.net/

Check it out...