You need to delete an associated registry key or else your back up would fail.
Backup fails due to registry key left by Symantec Endpoint Protection Auto-Upgrade
http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2009081016003348?Open&seg=ent
When auto-upgrade is first run on a machine, Symantec Auto-Upgrade agent service is created and it has the following subkey in registry: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Smcinst TYPE Name Data REG_EXPAND_SZ ImagePath C:\Program Files\Symantec\Symantec Endpoint Protection\SmcLU\Setup\smcinst.exe Once upgrade is completed successfully, C:\Program Files\Symantec\Symantec Endpoint Protection\SmcLU\Setup folder is removed. But the service and its associated registry key are left behind.
solution.
A workaround to allow backup program to complete successfully is to delete HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Smcinst subkey. However, please note that it will be recreated when auto-upgrade is run next time.