title: .NET using wrong 2.0 machine.config instead of 4.0
body: <p>I have a .NET web application install on IIS 7.0 Windows Server 2008 R1.  I have installed .NET 4.0 on the server and configured an app pool for 4.0 and integrated pipeline.  For some reason I am getting the following error:</p>
  
  <pre><code>(500.19) The configuration section 'system.web.extensions' cannot be read because
    it is missing a section declaration.
  </code></pre>
  
  <p>It appears that it is using the wrong <code>machine.config</code> file from V2.0 .NET rather than the <code>machine.config</code> file which has defined the <code>system.web.extensions</code> config section.  I proved this by replacing the <code>machine.config</code> file in the V2.0 framework with the one from the V4.0 framework and the web application no longer throws the <code>500.19</code> error.  I have tried to uninstall and reinstall .NET 4.0 as well as running <code>aspnet_regiis -i</code>.</p>
  
  <p>Any thoughts on why it would be trying to using the 2.0 <code>machine.config</code>?</p>