@Romulus:
I have to agree with IL here. Nova edition is usually known as 1st edition, while MB is the second or “Classic” edition.
Revised is notoriously known as 4th edition so the CD ROM one have to be the 3rd!!!
I understand that people tend to think of this as the case, but there are two problems with this approach.
Firstly, there are three distinct editions of the MB version of the game - 1984, 1986 and 1997 (CD Edition). Given that, in order to call Revised “4th Edition” and remain consistent with “edition numbers”, the Nova version would need to be called (as Imperious alluded to earlier) “Edition Zero”. If you’re going to acknowledge the 1997 MB 3rd Edition, ignoring the existence of the 1984 MB 1st Edition is simply inconsistent and inaccurate.
Secondly, the Milton Bradley editions were all changes to the rules only, not to any of the game components (except for a small map change in 3rd Edition). This makes all three MB editions basically tweaks to the rules of the same game. However, it can be argued that the Nova and AH versions of A&A are completely different games from the MB version, since the maps and the rules themselves are significantly different. I have heard this argument made many times.
Given all that, it just makes sense (at least to me) that the different publishers’ incarnations of A&A should be called “versions” and the separate releases of the games within each publisher be called “editions”, as I outlined above. This precendent has, in effect, already been established by Milton Bradley. Of course, everyone is free to draw his or her own conclusion from the facts at hand.