My New Xbox 360 has Xbox Live NAT problem

Ok so my Old lanch 360 is out so i bought myself a new 60GB pro 360 but at the moment im running my old 20Gb HDD on it i desided to try to conect it to xbox live an is dose but its restricted with the NAT settings.

it say i can change the setting in my router settings but heres the problem i dont have one my old 360 ran fine with it but this new one dosn't.

my modem it a speed Stream 4200.

im stumped

Do a google search with something like "port forwarding xbox 360 ______"

with "____" being the type of router you have. Customizing these settings will allow you to have a static connection to the router and should provide you with an open NAT.