good - - you've learned something on networking.
this last issue is why it's better to use IP Address Reservation than attempting to a setup manually - - it's just too easy to foul out. Then there's that DNS question as to 'what is the right DNS for me?'
That's all resolved easily and correctly even it you change ISPs via IP Address Reservation in your router rather than the TCP/IP settings.
Using your Belkin.3236 Router and assuming you have not changed the default IP address for Belkins: the default IP address is 192.168.2.1
put this into your browser as if it were a URL and hit enter.
you get a prompt for the admin-id/password
Belkin: Using a blank password you can login to Belkin router setup page ( leave the password space blank and hit enter ). The use of a blank password for login is not always a good idea, if you wish you can change the default password to a new password on the same page.
You need the MAC address of the Wired NIC or WiFi adapter you wish to be static.
(hint: get a connection to the router and then start->run->cmd and enter ipconfig /all)
The Physical address shown is the MAC address.
I can't seem to find your Belkin 3236 Router anywhere on the Internet - - are you sure you have the model number correct? Belkin model numbers (as I see them) start with Fxxxx