It has been quite sometime since the last Age of Empire came out. If I remember right it was the Asian Chiefs Expansion for AOE III a couple of years ago at least.
Now Microsoft Games has come out with a new version. The difference is that this is an online version and it is free to play!! Even though it is called Age of Empire Online, it actually requires an install (of around 60 MB) and also download a number of updates once installed. But it uses Live Online for Windows (equivalent of XBOX online for Windows Games) to store your games state and so you basically do not need to save anything on the local machine itself. But the catch is that you cannot save a game in the middle, but only save the state of your capital city.
Also this works on a free for initial play and then buy premium features. I just started playing last week and for people who have played any of the previous AOE version, most of the game play remains the same.
There are also quite a number of things that you can use only if you buy a premium pack and obviously that is where the money is..
Now that the Windows 8 Developer Preview is out, I got it installed on a VirtualBox instance. As I was reading thru some of the dialogs that popup during installation, I got a sense that since this is an early release, the developers got more freedom and have displayed a sense of humor in some of the messages. 
