How do you know you all have the same address?

If it was by visiting a site like www.whatismyip.com it will tell you the public IP address of your router which you will be sharing via NAT (Network Address Translation). Your local addresses (private side of the router) will be unique within the network.

Several ways to check the local address. Try opening a command prompt and typing:
ipconfig <Enter>
The resulting display will show you your local address(es)


--=-- My credo: If it's worth doing, it's worth overdoing - just ask my missus, she'll tell ya laugh --=--
You're only paranoid if you're wrong!