its not your computer, its your router.
preferably make your computer a static ip, like here
http://portforward.com/networking/staticip.htmafter that you need to port forward by logging into your router and forwarding the port your using for minecraft (Default 25565) to the static ip
most default router ip's are 192.168.0.1, 192.168.1.1, or 192.168.2.1 (google your router brand with "default ip" )
after you port forward you can uninstall the retarded hamachi and host the server just by running it
Humm I thiink I'll give it a try..