Hello,
Open a Command Prompt and run the command "ipconfig /all".
Do you see the external IP address you are trying to access there? If not, it sounds like your router would need to be configured to forward port 80 requests to your local network IP address (NAT).
If you do see the IP there, are you able to access the site using that IP on the server itself?
If you turn on your Windows Firewall and enable the "Log dropped packets" option, you will be able to view the Firewall log (default: C:\WINDOWS\pfirewall.log) and see whether or not the connection is being blocked.
Also, check your Bindings settings for your website. It could be that you just need to add the external IP address to the list, or have the site listen on * for testing.
Hope this help!
Brock Hensley
Technical Support Representative
http://www.ServerIntellect.comManaged Servers, 24x7 U.S. Support, Web Hosting Solutions.