[dnanian]

Actually, on the Mac, a given volume can usually act as the boot (start up) volume for many different Macs (of course, only one at a time). It's one of the cool things about the Macintosh and OSX.

But -- an "image" isn't a physical drive. It's a file, on a drive, that represents a volume -- but isn't "real", and thus can't be booted from.

When you restore the "image", you "expand" it from a single file to a whole set of files and folders on a physical drive. At that point, it's "real" -- and thus can act as a startup disk.

It's kind of like files in a Stuffit or ZIP archive vs. files on your drive. You have to "unstuff" (restore) the image to a real drive before you can use it.

Make more sense?