So I'm trying to play CnC Generals with another computer in the house, but the other computer is an entire floor above the router and my computer has no wireless card. So one computer is connected to the router wirelessly and the other is wired into it. But we don't see eachother in the Lan lobby
1. Make sure your games are allowed past the Windows firewall.
2. Make sure your router is not separating wireless and wired computers(some do this so check the settings. it may be called allow routing between zones). This can happen with routers that allow multiple wireless networks as well.
Can you see each other or ping one another(local ip)?