Remember old D&D? What, 3rd edition? Pah! Not 2nd edition AD&D either, nor 1st edition. Not even "original" Basic/Expert/Companion/Master/Immortal. I'm talking really original D&D, based off of Chainmail wargaming rules. OD&D! Read about it at Delta's D&D Hotspot, which discusses the development of a game system that is almost 35 years old. So you know, he really doesn't like what he's heard about 4th edition (and I think I agree with him).
More information on the pre-Blue Box history of the game is at the Museum of Role-Playing Games' Review of White Box D&D. For use in starting a game is Philotomy's OD&D Musings, thought you'd have to turn to eBay or other sources for full rules.