Undoing "Do Not Show Again"

When selecting a results set and copying, a dialog box pops up giving you the option to either copy the headers, do not copy the headers, etc.  It also gives you the option to not show the box again by selecting "Do Not Show This Box Again" or something like that. 

Several weeks ago I clicked this box, but am now wanting it to pop up again.  How can I do this, if at all?

Thank you