We are using IIS 6.0 on a Windows Server 2003 Standard Edition with
Service Pack 2.  This is not a clean install of Windows Server 2003,
but it was upgraded to from Windows Server 2000.

We are having problem running ASP.NET applications on this server.
HTML pages and classic ASP pages run with no problem.

We use ASP.NET 2.0.  We ran aspnet_regiis.exe -ua to remove all
versions of ASP.NET and then aspnet_regiis -i to install it many
times.  Each run of aspnet_regiis -i executes nicely with no problem,
at least no Failure message in the installation log, and no warnings
or errors in the event viewer.

In IIS configuration, we created a virtual directory for our ASP.NET
application, and we did select ASP.NET 2.0 on the ASP.NET tag for our
application.

Now, if we try to check out our ASP.NET test page, we always get a 404
error, i.e., Page not found error.  But we can check out hello.html or
hello.asp in the same path just fine.

We checked the configuration and verified that aspx files are
associated with the ASP.NET engine C:\WINDOWS\Microsoft.NET\Framework
\v2.0.50727\aspnet_isapi.dll.

Still no warning or error messages were found in the event viewer
after we attempted to check out our web page.

Sounds very weird, right?  Any hint?