title: CreateFile / WriteFile is not destroying contents of old file
body: <p>The old contents are not being wiped out.
  Instead the data is being written over, so I still see old contents.
  What did I not do?</p>
  
  <pre><code>hFile = CreateFile(fname, // open testfile.txt
      GENERIC_WRITE, // open for reading
      0, // do not share
      NULL, // default security
      OPEN_ALWAYS, // 
      FILE_ATTRIBUTE_NORMAL, // normal file
      NULL); // no attribute template
  
  dwBytesToWrite = buff.GetLength();
  WriteFile(hFile, buff.GetBuffer(100), dwBytesToWrite, &amp;dwBytesWritten, NULL);
  </code></pre>