title: How to stop Vim from writing onto system clipboard when visually selecting texts
body: <p>I am using Vim 7.4.423 on a Windows 7 machine.</p>
  
  <p>I notice that Vim will copy to system clipboard of whatever texts that I have "highlighted" through Visual mode. Is there a way to stop him from do this?</p>
  
  <p>The "overwriting of clipboard upon enter visual mode" does not differ whether I use mouse click or the <code>V</code>/<code>v</code> operator. Nothing on the system clipboard will be left once I enter the visual mode.</p>
  
  <p>PS: I did not find <code>mswin</code> in my <code>_vimrc</code>.</p>
  
  <p>Thank you!</p>