(adsbygoogle = window.adsbygoogle || []).push({});I found this a couple of days ago its really easy... this works for me and my mates so don't groan if it doesn't for you BJ:
1.Put in MW3 and go to online menu
2.Press eject and take the MW3 disk out and put MW2 disk in
3.Play a game on MW2 and just get a kill or two
4.Leave the game and press eject and Put MW3 back in
5.Go to the online menu and you should have OPEN NAT TYPE
6.ENJOY!!