unit Unit1;

interface

uses
   Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
   Dialogs;

type
   TForm1 = class(TForm)
     procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
       Shift: TShiftState; X, Y: Integer);
     procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
       Y: Integer);
     procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
       Shift: TShiftState; X, Y: Integer);
     procedure FormCreate(Sender: TObject);
   private
     { Private declarations }
     oldtop, oldleft : Integer;
     dragging : Boolean;
   public
     { Public declarations }
   end;

var
   Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
   Shift: TShiftState; X, Y: Integer);
begin
case button of
   mbleft:
   begin
     oldleft := x;
     oldtop := y;
     dragging := true;
   end;
else Exit;
end;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
   Y: Integer);
begin
   if (dragging) then
   begin
     Form1.Left := Form1.Left + X - OldLeft;
     Form1.Top := Form1.Top + Y - OldTop;
end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
   Shift: TShiftState; X, Y: Integer);
begin
   dragging := False;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
   dragging := False;
end;

end.