//Oculta a barra de tarefas do Windows e a repõe:

//Oculta
void __fastcall TForm1::Button1Click(TObject *Sender)
{
ShowWindow(FindWindow( "Shell_TrayWnd" , NULL), SW_HIDE);
}

//---------------------------------------------------------------------------
//Mostra
void __fastcall TForm1::Button2Click(TObject *Sender)
{
ShowWindow(FindWindow( "Shell_TrayWnd" , NULL), SW_SHOW);
}