One of the causes of Norton 360 not showing one of your (assumed) internal hard drives could be in Windows Management Instrumentation (WMI) which Norton 360 uses in order to get information about hard drives installed in your PC. The easiest way to check if this is a problem is to go to Computer Management console and check Disk Management under Storage (right click onto your computer icon on your desktop and clicking onto Manage). It may be that the hard drive in question is not showing properly there which is directly causing Norton 360 not to show it in its Backup and Restore tab. From here you can try with Refresh or Rescan disks in order to bring things in order. Please note that even Windows Explorer does not use WMI when it shows your drives. Therefore, that may confuse many people as they would assume all is fine with their Windows OS while it actually is not as WMI information got corrupted.