I am setting up a new windows 2003 server and I was pulling my hair out trying to figure out how to get my aspx page to show up in the browser. I kept getting a page not found 404 error for every aspx page but not .html pages.
So, I opened up IIS manager and went to Webservice Extensions and noticed that ASP.NET was prohibited. So I right clicked on it and set it to be allowed. In Windows 2003, all the webservice extensions are prohibited by default to ensure security.
Hopefully this will save someone some time when configuring a new windows 2003 box.