title: Select-String fails with search term containing special characters
body: <p>When I run:</p>
  
  <pre><code>$SearchStr = "c:\programFiles\xyz"
  Select-String -pattern $SearchStr -path $env:SystemRoot\win.ini
  </code></pre>
  
  <p>I get an error message stating that the string is "not a valid regular expression"</p>
  
  <p>By contrast, it is working fine when <code>$SearchStr</code> doesn't contain special characters.</p>
  
  <p>Why doesn't it work with special characters such as <code>\</code>?</p>