将窗体显示在 PageControl 上

var
   AWinControl:TPageControl;
begin
  AWinControl  :=  PageControl1;
  if frmAbout = nil then Exit;  
  frmAbout.ManualDock(AWinControl, nil, alClient);
  frmAbout.Align := alClient;
  frmAbout.Show;
end;

http://www.cnblogs.com/jxgxy/archive/2010/02/13/1668082.html