Okay, So i'm kinda pissed cos I bought this game here with the expectation that I could just boot it up and play with my friends over the internet. But, I first had to find a multiplayer CD key, and now I can't play online because my executable differs from theirs (the host is running off the hard copy). What do I have to do so I can just play the game with my friends, and not have to find all these crazy solutions to problems that never should've arisen in the first place.

The new versions of the game have had the Multiplayer ripped out entirely. The modified EXE thing is not that your exe is any different then the hosts, it's just that special code has been put in to make sure it doesn't work. They did the same thing with all newer copies of Rise of Nations and Age of Mythologies. This mostly has to do with the pure lazy attitude towards the PC as a gaming platform.

On the GOG page it clearly shows (or not so clearly) that the only game modes listed are Single Player.

I'm sorry that there is not much you can do in this situation, other then hunt down an original copy of the game (the modern physical copy re-releases have the same issue as this version does)

This whole thing pisses me off just as much as it pisses you off.

I noticed Empire Earth has multi player in its description, but the second one does not... Is this counting LAN as well?

I just bought EE2 and multiplayer is working fine! Just login with your Gamespy details.

I don't think this is correct. For Age of Mythology, at least, no code was changed. The new distributors just stopped providing valid CD keys for online play using the ESO service. LAN and Direct Connect still work fine, and the game is very popular on GameRanger.