How do I play Age of Empires multiplayer on Windows 7?

AOE on my windows machine is unable to detect games setup by my peers (Windows 7) on the same network (LAN) or on the internet.

Is there something I should be doing (patch, fix) to join others with Windows 7/Vista?

I can see you've tagged this AOE 2 - we play LAN games of AOE 2 in our office network successfully with a mixed environment of Windows 7/XP machines. We did notice some issues with the colours in AOE on Windows 7 that were related to a clash with the windows theme - you can see the solution for that at: http://social.answers.microsoft.com/Forums/en-US/vistagaming/thread/a1763d12-11e2-498f-9b23-122792b14f74

With the networking, the only issue we saw was that the Windows Firewall blocked outgoing/incoming connections by default and we had to add exclusion rules for it, by clicking 'Unblock' in the dialog that pops up when the game runs. You would need to 'Alt-tab' out of the game to hit 'Unblock'.

Edit: Also, I have seen success disabling extra networks (wireless, lan, hamachi) when you're trying to play. Sometimes, for whatever reason, an unused/enabled lan network keeps you from connecting with your wireless one. Hamachi is great if you're using it but should be disabled when you're not.

Game Ranger allows players to connect to certain games with multiplayer issues, such as AOE 2 and its expansion.

You can if you use a router, go into the settings of the router and check off UPnP and check if your firewall is not blocking Age of Empires 2.