procedure TForm1.SetClose(ExistClose: boolean);
var MENU,Style:uint;
begin
  style:=getclasslong(handle,gcl_style) or cs_noclose;
  if existclose then style:=style and not cs_noclose;
  setclasslong(handle,gcl_style,style);
  menu:=GetSystemMenu(handle,ExistClose);
  if not ExistClose then begin
    removeMenu(menu,SC_CLOSE, 0 );
    removeMenu(menu, 0 , 0 );
  end;
  RedrawWindow(handle, 0 , 0 ,RDW_FRAME+RDW_INVALIDATE+RDW_UPDATENOW);
end;

procedure TForm1.WM_NCCREATE(var message:tmessage);
begin
  inherited;
  SETCLASSLONG(handle, GCL_STYLE, GETCLASSLONG(handle, GCL_STYLE) or CS_NOCLOSE);
end;