The hardware address is located on the underside of the laptop. Your old Ethernet cable might still work if you plugged it into your router, but it will only display the IP address, not the MAC address. To locate MAC Address in Windows 7-8/10- this option isn’t available from Settings>Network and Sharing>Public Network that is for connecting to a WiFi network. You have to do it from Control Panel>View network connections >Statistical Details >look for “hardware addresses” >Double click on one value to open a new window with all values including “current state”. Look for headlines such as Wireless Network Connection or Ethernet Connection and find where HW Address starts with “00:17”.