title: Microsoft.Expression.Drawing.Aero missing (what is it?!)
body: <p>I have a window and I created a "callout" there. When I try to create the new window with <code>this.InitializeComponent();</code> I get an exception:</p>
  
  <blockquote>
    <p>The assembly with display name 'Microsoft.Expression.Drawing.Aero' failed to load in the 'Load' binding context of the AppDomain with ID 1. The cause of the failure was: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Expression.Drawing.Aero, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.</p>
  </blockquote>
  
  <p>How can it be? What is Microsoft.Expression.Drawing.Aero?</p>