In the IIS, Web Site properties, ASP.NET tab, ASP 2.0.50727 is selected with the Virtual Path /DotNetNuke.
I believe that there may be 'something' with the Default.aspx file, or so reports Visual Web Developer 2005 Express-
Line #1 – <%@ Page Language="vb" AutoEventWireup="false" Explicit="True" Inherits="DotNetNuke.Framework.DefaultPage" CodeFile="Default.aspx.vb" %>
Error - withEvents variable ‘Form’ conflicts with property ‘Form’ in the base class ‘Page’ and should be declared ‘Shadows’
Line #3 - <asp:literal id="skinDocType" runat="server"></asp:literal>
Error – Unrecognized tag prefix or device filter ‘asp’
Line #23 - <dnn:Form id="Form" runat="server" ENCTYPE="multipart/form-data" style="”height: 100%;">
Error – Element ‘Form’ is not a known element. This can occur if there is a compilation error in the web site.
‘Errors’ in the file Default.aspx file as so reports Visual Web Developer 2005 Express Edition. This file found in the ‘root’ directory of the extracted files of DotNetNuke.4.5.1.