A: 

Am I assuming correct in that you have a hidden folder under your virtual directory?

If so, the hidden folder should still show up in IIS. You need to fake the folder as a virtual directory, which gives you access to the Configuration button and remove wild card mappings. Then Remove the folder as a virtual directory.

David Liddle
It's not a hidden folder under the virtual directory, it's the standard Windows administrative share that is apparently being accessed through Windows Explorer via \\server\c$
Rob
+1  A: 

Add in the config

<location path="HiddenFolder">
  <system.web> 
    <authorization>
      <deny users="*" />
    </authorization>
   </system.web>
</location>

And add ignore routes to your routes map:

routes.IgnoreRoute("[HiddenFolder]");
zihotki