redirect=index.php   
cookie_test=xxxxxxxxxx
login_username=MyUser
login_password=MyPass     
autologin=on          
login=Вход

procedure TForm1.Button1Click(Sender: TObject);
const
  fact:shortString = 'http://torrents.ru/forum/login.php';
var
  fGet,fPost:TStringList;
begin
  fGet:=TStringList.Create;
  fPost:=TStringList.Create;
  IdHTTP1.AllowCookies:=true;
  IdHTTP1.CookieManager:=IdCookieManager1;
  IdHTTP1.HandleRedirects:=true;
  With fPost do
  begin //with
    Add('redirect=index.php');
    Add('cookie_test='); //òóò õç ÷òî ïèñàòü
    Add('login_username=MyUser');
    Add('login_password=MyPass');
    Add('autologin=on');
    Add('login=Âõîä');
  end; //with
  fGet.Text:=IdHTTP1.Post(fact,fPost);
  If fGet.IndexOf('Âû çàøëè êàê') <> - 1 then
    MessageBOX(Application.Handle,'Çàëîãèíèëèñü!','Óäà÷íî!',mb_OK)
  else
    MessageBOX(Application,Handle,'Îøèáêà!','Íåóäà÷íî!',mb_OK);
  IdHTTP1.Free;
  IdCookieManager1.Free;
  fGet.Free;
  fPost.Free;
end;