"In addition, it is possible to completely erase a hard drive and install Snow Leopard without a pre-existing operating system in place, enabling users to bypass the possible headaches of an upgrade and go with a clean install instead." I'm a newbie here but wonder if the above AppleInsider statement is true. I installed Snow Leopard over my existing Leopard w/out a hitch. Earlier OS X retail DVD versions clearly distinguished between "Install" and "Upgrade" - correct?. I'm confused where I read Snow Leopard required an existing OS (Leopard or Tiger) to install. It appears Snow Leopard is a "full install" DVD?