I have a windows 8.1 laptop with 2 identical (Dell) monitors connected. However, I would like to be able to switch the second screen on or off by preferably one click or Crtl-etc pressing. I have no idea how to make that work from windows. Not sure this is the right place for this question; however if you know the answer, I would really appreciate your comment. Thanks.
Microsoft support is a great place for questions on Windows functionality and keyboard shortcuts.
That said, there is usually a function key combo on laptops to turn on the second screen. Hold down the FUNCTION key button and look for a key on the laptop that has a screen symbol. Dell is also a great place for this type of question.