I am not sure if I have read this correct so forgive me if I am wrong.
You say you are trying to use the password 'Admin'. Are you sure this is the correct password. Those are the usual passwords for the router settings home page. But you need to log onto the network before you can access that page.
If it is WEP protected the password will be either 10, 26 or 58 characters long depending on the encryption used.
I personally prefer WPA security because the password can be a lot more flexible (and WPA is less crackable).
Stick