On the so called GM Build I Formatted my drive and did a clean install.
SL is an upgrade from Leopard.
Upgrading from Mac OS X v10.5 Leopard.
If your Intel-based Mac is running Mac OS X v10.5 Leopard, just purchase Mac OS X v10.6 Snow Leopard and follow the simple installation instructions.
Upgrading from Mac OS X v10.4 Tiger.
If your Intel-based Mac is running Mac OS X v10.4 Tiger, purchase the Mac Box Set, which is a single, affordable package that includes Mac OS X v10.6 Snow Leopard; iLife 09, with the latest versions of iPhoto, iMovie, GarageBand, iWeb, and iDVD; and iWork 09, Apples productivity suite for home and office including Pages, Numbers, and Keynote.
http://www.apple.com/macosx/specs.html