If you are running windows vista or windows 7 you should be able to into network and sharing center in the control panel. Here you can click view full map to see all computers connected to the network. Of course, you could always go into your router page by typing 192.168.0.1 in your browser. If you've created a password type that, otherwise the password is usually "admin". Click the status tab at the top and and scroll down to see the names of computers or devices connected.