dephi中单击鼠标拖动窗口（使用WM_SYSCOMMAND）

 procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  ReleaseCapture;
  Perform(WM_SYSCOMMAND,$f012,0); //开始拖动窗体
end;

http://blog.csdn.net/diligentcatrich/article/details/7008516