The Following example demonstrates checking if full windows drag is enabled.

Example:
procedure TForm .Button Click(Sender: TObject);
var
  b : bool;
begin
  SystemParametersInfo(SPI_GETDRAGFULLWINDOWS, 0, @b, 0);
  if not b then
    ShowMessage('Full Window Drag is not enabled') else
    ShowMessage('Full Window Drag is enabled');
end;