系统自带的那个实在是太慢了....用下面这个替代掉
function DelDirectory(const Source: string): Boolean;
var
  fo: TSHFILEOPSTRUCT;
begin
  FillChar(fo, SizeOf(fo), 0);
  with fo do
  begin
    Wnd := 0;
    wFunc := FO_DELETE;
    pFrom := PChar(Source + #0);
    pTo := #0#0;
    fFlags := FOF_NOCONFIRMATION + FOF_SILENT;
  end;
  Result := (SHFileOperation(fo) = 0);
end;