I don't know why Badspot's tutorial tells you to change all this DNS and gateway stuff but you shouldn't have to change anything on your computer (minus anti-virus/firewalls) to make port forwarding work. Leave your IP options to Obtain Automatically or whatever, and setup your router as normal going to your computer IP. Then if there's a LAN IP Reservation section in your router, configure that to always give your computer the same ip. If there isn't, you'll just have to check your IP each time you start a server and change the router to use that one.