Jeffrey, the only way to know what the exact error says is to do exactly what the message in your post says. Edit your web.config and change the customErrors mode to Off. Then when you hit the site you'll see the actual error and then we can begin to help you.

Here's the error Message:

Server Error in '/portal' Application.

Data at the root level is invalid. Line 1, position 1.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Xml.XmlException: Data at the root level is invalid. Line 1, position 1.

Source Error: 
The source code that generated this unhandled exception can only be shown when compiled in debug mode. To enable this, please follow one of the below steps, then request the URL:

1. Add a "Debug=true" directive at the top of the file that generated the error. Example:

  <%@ Page Language="C#" Debug="true" %>

or:

2) Add the following section to the configuration file of your application:

<configuration>
   <system.web>
       <compilation debug="true"/>
   </system.web>
</configuration>

Note that this second technique will cause all files within a given application to be compiled in debug mode. The first technique will cause only that particular file to be compiled in debug mode.

Important: Running applications in debug mode does incur a memory/performance overhead. You should make sure that an application has debugging disabled before deploying into production scenario.

[XmlException: Data at the root level is invalid. Line 1, position 1.]
   System.Xml.XmlTextReaderImpl.Throw(Exception e) +90
   System.Xml.XmlTextReaderImpl.Throw(String res, String arg) +127
   System.Xml.XmlTextReaderImpl.ParseRootLevelWhitespace() +1953906
   System.Xml.XmlTextReaderImpl.ParseDocumentContent() +503
   System.Xml.XmlTextReaderImpl.Read() +41
   System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace) +145
   System.Xml.XmlDocument.Load(XmlReader reader) +96
   System.Xml.XmlDocument.Load(String filename) +160
   DotNetNuke.Modules.Admin.ResourceInstaller.ResourceInstaller.InstallPortal(String strFile, Boolean writeFeedback, Int32 indent) +291
   DotNetNuke.Modules.Admin.ResourceInstaller.ResourceInstaller.Install(Boolean writeFeedback, Int32 indent, String type) +961
   DotNetNuke.Services.Upgrade.Upgrade.InstallDNN(String strProviderPath) +747
   DotNetNuke.Services.Install.Install.InstallApplication() +391
   DotNetNuke.Services.Install.Install.Page_Load(Object sender, EventArgs e) +274
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +47
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436

Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433