I just found this on the web i thought it might be useful to some people.
Getting to the terminal is easy: while you're sitting in the chair in the main menu, hit the left and right triggers on your controller a few times. L, R, L, R, L, R, L, R, L, R! From there, the only thing to do is to head to the back of the room and find the small terminal computer. Typing in the DOA command (and then pressing enter) unlocks Dead Ops Arcade (located in the main Zombies menu once unlocked); entering the command ZORK launches the classic text adventure, Zork.