■ Choose <Yes> only if you are sure that by overwriting
    the contents of the document on disk with the contents
    of the document in memory, you won't lose valuable
    information.
  ■ Choose <No> to redisplay the dialog box and enter a
    unique filename for saving the current document.
  ■ Choose <Cancel> to cancel the Save As or Exit command,
    and return to your document.