By design, when you use Navigateurl, supplying a value for key, the control that matches the value of key from the Module definition is loaded into the admin skin by itself.  For example " use: 'registerUrl = NavigateURL("Register")' then 'Response.Redirect(registerUrl, True)'"  loads the admin skin and displays the ManageUsers.ascx user control.

That's the way it's supposed to work.

If you created a module definition with a control that had the key "MyKey" then calling response.redirect(navigateurl("MyKey"),True) would load the admin skin and only the user control defined in the module definition corresponding to that key.

Now for you to load different views of a module in a skin pane , one option is outlined in the post  http://www.dotnetnuke.com/Community/ForumsDotNetNuke/tabid/795/forumid/110/threadid/46342/threadpage/2/scope/posts/Default.aspx

It demonstrates dynamically loading different user controls (module views) into the same pane and skin view, while still displaying the other modules.

 Hope that helps.