title: cannot install visual studio 11 preview
body: <p>I use vista sp2 and have vs 2005/8/10 installed.</p>
  
  <p>I try to install vs 11 preview using the web installer but immediately get a message "setup blocked" (see image). the linked log just has many lines like</p>
  
  <pre><code>[1424:1894][2011-09-17T22:13:51.749+02:00]: Detected package: netfx_dtpmsi_1048, state: Present, cached: No
  </code></pre>
  
  <p>any idea?</p>
  
  <p><img src="https://i.stack.imgur.com/0Z2F3.jpg" alt="enter image description here"></p>