Gone, for example, is the old Clean Install option-which moved your existing OS and system add-ons to a Previous Systems folder and installed a fresh copy of the OS, requiring a good amount of tweaking and transferring of files afterward. While older versions of OS X made you decide what kind of installation you wanted to perform before you even specified what to install, Snow Leopard’s installer gives you a single installation path.
With Snow Leopard, Apple has streamlined and simplified the process of installing Mac OS X.