Internet Connection Sharing and/or Internet Connection Firewall is currently enabled for a network connection, and must be ...

Internet Connection Sharing and/or Internet Connection Firewall is currently enabled for a network connection, and must be disabled before adding the Network Address Translation (NAT) routing protocol.
To disable Internet Connection Sharing and/or Internet Connection Firewall, go to the properties sheet for the connection in the Network Connections folder. Clear the appropriate checkbox on the Advanced tab.