[dnanian]

Actually, this isn't something you can do. While you can use a Sandbox to preserve an existing version of your OS (while you run from the Sandbox), you can't modify a non-Sandbox and expect to be able to restore a Sandbox "over" it -- it'll roll back too many things partially (as opposed to the opposite, where you'd be either booting back to an older setup, or *updating* things by applying the changes made to the Sandbox to the main volume).

I think, if this is something you're worried about, that I'd invest in an external FireWire CD/DVD drive...