This is too incomplete to make any suggestion. Say what the Exact error message is.
So far, I can only guess that the error is reporting there is another computer using the IP address your computer is using...(or trying to). This is only my guess. You have a static IP address locked in on one or both computers and since the router cannot issue a new address, Windows blocks your machine from causing the network to fail.
To disable your WAN mini-port will dis-connect you from the network and internet.
If you do in fact want to remove the WAN Mini-port, go to the control panel, double-click the Add/Remove programs icon, wait for list to fill and then look for your Mini-port driver in the list and uninstall it.