o if x is CW_USEDEFAULT (or CW_USEDEFAULT16) and y is *not*
  CW_USEDEFAULT (or CW_USEDEFAULT16) then use y as a second
  parameter to ShowWindow(). Some apps (CALC.EXE for Win98
  is one of them) use this undocumented feature to create
  hidden window with WS_VISIBLE style set.