Old D&D is pretty basic stuff. For example, with the really old stuff, races and classes were one. Alignment is just chaos and law (no good and evil). That was changed in later supplements.
1E AD&D is one of the hardest games to master because of the way the rules are written (if you're looking to play RAW..rules as written). I disagree with the post above that says that 1E AD&D is easiest straight out of the box. I would say that person has been playing with a lot of house rules.
I mean, take a look at the combat section in the 1E AD&D DMG. The 1E combat round is one of the most complicated, still hotly debated topics every to come out of D&D.
If you're interested in older versions of the game, check out this forum:
DRAGONSFOOT . There are lots of helpful folks there that can help you out with 1E or 2E AD&D. Even some of the original TSR game contributors hang out there--someone answer your questions there could be the person who wrote the rule you're asking about!
2E AD&D is probably where I would point you. It's a tad less crunchy than 3E, but still has a lot of crunch for those that like it. The rules are, for the most part, more coherent than what you see in 1E (don't get me wrong, I love 1E--the rules are just a mess, though).
2E was written from two perspectives, and it does a good job of having a foot in each type of gaming. First, there's the crunchy 1E people (and the 3E people) who like to play the game like a miniatures war game with a grid and such. But, 2E is also written for the group that doesn't use a grid in combat at all. They just sit around the gaming table, listening to the DM's desription, reacting to what he says, not worrying about exact distances on a map. 2E can be a faster paced, more visually abstract game, if you play it that way.
There are plenty of supplements for 2E, though, that add in more crunch. First, additional things you can do with your non-weapon proficiency slots pop up (similar to skill points in 3E), and then, books that tie the game back down to the graph are given.
You decide how you want to play, though, which is the beauty of 2E--it's flexibility.