title: Strip all characters after a delimiter in filenames
body: <p>I have filenames in a directory in the format of "APP_ENTITY_part___20120910.txt"</p>
  
  <p>I would like to strip off everything after the 3 underscores and keep the first portion of the filename.</p>
  
  <p>Is there a good website that could direct me in how to accomplish this?  </p>
  
  <p>Or, maybe one of you dos batch experts can lead me in how to do this?</p>