title: Visual Studio configuration problem after upgrade to VS2010 / XNA 4
body: <p>I'm attempting to migrate a project from XNA 3.1 in VS2008 to XNA 4 in VS2010.</p>
  
  <p>I realise that there will need to be some code changes, but the problem I am currently facing is that, having been through all project properties attempting to ensure that any references to the old XNA are removed and that appropriate references to XNA 4 are added, I am getting build errors such as</p>
  
  <pre><code>The type 'Microsoft.Xna.Framework.Vector4' is defined in an
  assembly that is not referenced. You must add a reference to assembly
  'Microsoft.Xna.Framework, Version=3.1.0.0, Culture=neutral, 
  PublicKeyToken=6d5c3888ef60e27d'.
  </code></pre>
  
  <p>and</p>
  
  <pre><code>Cannot implicitly convert type 'Microsoft.Xna.Framework.Vector4 [c:\Program Files (x86)\Microsoft XNA\XNA Game Studio\v4.0\References\Windows\x86\Microsoft.Xna.Framework.dll]' 
  to 'Microsoft.Xna.Framework.Vector4'
  </code></pre>
  
  <p>Following the declarations of the <code>Vector4</code>s being referred to by the latter error, I can see no evidence that either of them should be any different...</p>
  
  <p>I've tried using Agent Ransack to find which files contain the <code>6d5c3888ef60e27d</code> key, and killed a few <code>Content.contentproj</code> files etc just in case, but thus far haven't found anything all that useful.  I must admit that since first encountering this problem I haven't been very thorough in tracking exactly what I've changed; I might try reverting to an old version where everything worked under VS2008 and going through the process again.</p>
  
  <p>The configuration of the project is somewhat different from a normal XNA game I suppose, and there are C++ elements to it, in case that's relevant.</p>