procedure TForm1.Button1Click(Sender: T);
var
  DirInfo: TSearchRec;
  r : Integer;
begin
  r := FindFirst("C:\Download\Test\*.*", FaAnyfile, DirInfo);
  while r = 0 do begin
 if ((DirInfo.Attr and FaDirectory <> FaDirectory) and
        (DirInfo.Attr and FaVolumeId <> FaVolumeID)) then
 if DeleteFile(pChar("C:\Download\test\" + DirInfo.Name))
         = false then
 {Si no puede borrar el fichero}
       ShowMessage("Unable to delete : C:\Download\test\" +
                   DirInfo.Name);
    r := FindNext(DirInfo);
  end;
  SysUtils.FindClose(DirInfo);
  if RemoveDirectory("C:\Download\Test") = false then
 {Si no puedes borrar el directorio}
    ShowMessage("Unable to delete dirctory : C:\Download\test");
end;

Speed test