Quem sabe o que mais está faltando? A melhor opção pode ser reinstalar o sistema operacional. Ele entrará no modo Arquivar e Instalar , conforme discutido em em o blog da Apple :
Should one need to archive and install (which is where your previous system files are archived in a separate location and a new system is installed in their place), the installer will it automatically [sic] when it detects an attempt to install the same operating system as is currently found on the Mac. When installation is complete, Snow Leopard cleans up after itself and doesn’t leave users with an ugly “Previous System” folder as before.