Resolved the issues looking at the post that was just made that put light on the problem.

Go to the download.vb file and you will need to make 2 fixes.

Search for "Web.IHttpHandler"
 

and replace with

"System.Web.IHttpHandler"
 

file is found here:
DotNetNuke\App_Code\XML\Handlers\download.vb

 lines 31 and 89

Fixed the issue thanks for the post made on the other topic.

So you changed, then saved and restarted the website, and still had error on line 34 after changing like this:

From:

Line 34:         Private Sub RenderToResponseStream(ByVal Response As Web.HttpResponse, ByVal controller As XmlController)

TO:

Line 34:         Private Sub RenderToResponseStream(ByVal Response As System.Web.HttpResponse, ByVal controller As XmlController)

And then again on the next line mentioned there is a System.Web is being called without System with an error that will pop up if you rerun website.com/Install/Install.aspx page?

I fixed the one it took me to the next error, so then I changed it and it ran smoothly.  Not sure what modules you have in this folder (Folders in the App_Code folder)?

And can you print your entire page error?

Are you editing this file with notepad directly on the server?  Maybe a cache thing if your editing it and it is staying the same because the error message should change somewhat if it is reading it correctly.

How can we fix it if we didnt know about upgrading XML first??