i have IIS on a Win XP Pro system. the router points port 80 to that system. when i try & access from a PC on the Network, i can see my test page. when i try to access from a PC outside my network I get an error message and the page is not displayed. any ideas??

What is the error message you get? Error messages generally give you a good clue as to what might be the problem. You can see it, we cant. Stuart

It turns out that my modem blocks ports 25 & 80. i need to upgrade my service to unblock these ports. thanks.

It is not your Modem blocking the ports, Modems don't do that, routers do. Have you forwarded port 80 from the router to the web server? Failing that it could be your ISP. Port 80 is the default port for Web pages. Some ISPs block port 80 which prevents you from running a Web server. This is to cut down on excessive bandwidth. Port 25 is often blocked as an anti-spam measure. Your only solution in this case is to to talk to your ISP and ask them to unblock the ports or to change your ISP to one that does allow web servers. Stuart

Yes, that is the problem. When i spoke to my ISP yesterday, they said it was the modem, but it could be that they do it on their end. My router does have port 80 fowarded which is why it works from an internal PC. I need to upgrade my service in order for them to open port 80 & 25. The reason they do this is, as you said, to prevent people from having web servers at home sucking up bandwith. Thanks