If and when the hard disk gets wrecked, that's when you get a new one to get the computer running again.
Aye a "clone" of your drive, that is the description of a full snapshot of your system.
Or, if you have the original install disks then you can use them without the need to clone anything, it is the same system regardless of the licence used: but then you'd have to restore your data backup. You will presumably have the licence number saved somewhere and simply enter it in during the install when requested.