Open Computer>>Network.
This will show you all the PC's connected to your network, but not all devices. You also won't have detailed information such as MAC's and IP's
There a few programs that allow you to view that info from within Windows 7, but they're sketchy and most times not free.
As ickymay suggested, find out the IP to your gateway/router/hub (by right clicking and going to status, click details and take note of IPv4 Default Gateway) type the IP in your browser and take a look around - varies by model/firmware but there should be a place somewheres that you can do that.