Restore Failure - what do you think ?

[The Grandfather]

I am experiencing some problems , and want to restore my system copy I have backed up on an external HDD ( WD firewire ,Mac OS Extended Journaled ) to my Mac, in the past I made a full system copy using Super Duper, and now want to install it back on my Mac , Ive re booted while holding the option ( alt ) key and the Mac is now running from my external HDD back up copy, ive just opened up the Disk Utility ,and ive entered my external HDD in the Source box, and entered my internal HDD in the Destination, and ticked Erase destination. When I click Restore , I get this message ..

Restore Failure

could not erase target - Operation not permitted

any advice Please

 

[Jethryn Freyman]

Try using Disk Utility to erase and reformat the hard disk in your Mac.

 

[The Grandfather]

Try using Disk Utility to erase and reformat the hard disk in your Mac.

Thanks, I am just wondering if I do that, and find that there's some thing wrong with my backup copy already on my external HDD, and I can't transfer it to the now erased internal HDD, I would be stuck