[Nyctos Kasignete]

Код:

...

type
  TForm1 = class(TForm)
  private
    { Private declarations }
    procedure WMSYSCOMMAND(var Msg: TMessage); message WM_SYSCOMMAND;
    procedure WMWINDOWPOSCHANGING(var Msg: TMessage); message WM_WINDOWPOSCHANGING;
  public
    { Public declarations }
  end;

....


procedure TForm1.WMSYSCOMMAND(var Msg: TMessage);
begin
  if (Msg.WParam <> SC_MAXIMIZE) and
     (Msg.WParam <> SC_MINIMIZE) and
     (Msg.WParam <> SC_CLOSE) then inherited;
end;

procedure TForm1.WMWINDOWPOSCHANGING(var Msg: TMessage);
var
  wp: PWindowPos;
begin
  wp := PWindowPos(Pointer(Msg.LParam));
  wp^.flags := wp^.flags or SWP_NOMOVE;
  Msg.LParam := Integer(wp);
  inherited;
end;