404 when page exists - IIS 5, ASP.NET 4.0

I have a webserver running Server 2003 Datacenter and IIS 5 which is hosting a variety of ASP.NET 2.0 websites. I'm attempting to add an ASP.NET 4.0 website which I wrote via the VS2010 Beta, and I have .NET 4.0 Beta 1 installed on the server.

The website appears to be configured correctly; anonymous access is on, it points to the right folder, and is set to asp.net 4.0.

Why might it be giving me a 404 error when I browse to it, both locally and remotely?

Is logging turned on? If it isn't, turn it on. If it is on, check to see of a corresponding entry is written to the log file, and check to see if all its details match up.

If no entry is being written, then it's possible that the wrong website in IIS is serving the content for your request (check the hostname it's listening on).

Lastly, are you sure it's IIS 5? I thought 2003 shipped with IIS 6?

404 Substatus 2 in IIS means: "Web service extension lockdown policy prevents this request.", the more friendly message on IIS7 for 404.2 says "The page you are requesting cannot be served because of the ISAPI and CGI Restriction list settings on the web server."

Check out the follow KB articles for possible fixes:

http://support.microsoft.com/kb/328419/ http://support.microsoft.com/kb/328505/ http://support.microsoft.com/kb/328360/

In IIS6 and 7 the http sub-statuses contain important information, for a full list check:

IIS5 and 6 : support.microsoft.com/kb/318380

II7: support.microsoft.com/kb/943891

You just need to enable the web extension for ASP.NET 4.0 in IIS.

Is the DNS name pointing to the right server?