Installing Snow Leopard over Leopard?

[SephirothXR]

Will it install like the OS does on the iPhone, as in the existing data isn't put in a new folder? What exactly happens when you install a new OSX?

 

[Snowbound]

When you install a new OS, it gives you the option to simply upgrade and keep all of your information as is, or to reformat and wipe out everything. So whichever you want to do is possible.