title: Error from graphviz in python (windows 7)
body: <p>I have a problem with graphviz in python, here is what happened:
  I tried to produce some plot from python using graphviz, but I got the error message:
  "<strong>RuntimeError: failed to execute ['dot', '-Tsvg', '-O', 'Digraph.gv'], make sure the Graphviz executables are on your systems' path</strong>"</p>
  
  <p>I installed graphviz on windows, however, every time I install it (install process is fine), it always installed on root directory of the secondary drive (not C drive), I add the dot.exe directory to system path, but nothing happened, I'm not sure how these problems related, Is there anyone can help?</p>
  
  <p>I am using my work computer but I have admin rights.  </p>
  
  <p>Thank you.</p>