I am reliably told the best way to make a perfect one to one clone is this: Have two matching sized new disks available. Install the OS / apps / files / etc on disk one. Install the OS on the second disk and at the first setup dialogue, when asked "would you like to copy from another Mac/Disk/TM Backup?" Select the first new installed system and copy "ALL" data. ( has to be done at this point for a one to one copy ) Is there any better way to have 2 x exact systems, and if a problem occurs just swop the drive over .... done, working no re-installs whatsoever ?? Thanks, Marty.