title: IThumbnailProvider and IInitializeWithItem
body: <p>I am trying to develop an <code>IThumbnailProvider</code> for use in Windows 7. Since this particular thumbnail would also be dependant on some other files in the same directory, I need to use something other than <code>IInitializeWithStream</code> to a path to work with, this being <code>IInitializeWithItem</code>. (Alternatively, I could use <code>IInitializeWithFile</code>, but that is even more frowned upon apparently.)</p>
  
  <p>No matter what I do, I cannot get it to work. I have Microsoft's <code>FileTypeVerifier.exe</code> tool which gives the green light on using <code>IInitializeWithItem</code>, but when explorer calls it, it only seems to try <code>IInitializeWithStream</code>, ever. (This was tested by temporarily implementing said interface, and Beep()ing away in its <code>Initialize()</code>) Did I forget to configure something?</p>
  
  <p>In short: how do I get this to work?</p>