LiveDosGames is a free, portable, fast Linux Operating System, which contains old, but legendary Dos games. It's small, so it can be stored on an USB stick, but it doesn't mean that it doesn't contain the everyday, general programs(Media Player, Picture Viewer etc.). If you would miss something(Games, different editors etc.) then with a click you can activate it, and it automatically puts itself to the menu, it doesn't need any installation and configuring.
Please visit livedosgames.com for more information! (There's an list of avalible games)