If agent was installed as a package it needs to be uninstalled. Only
Server software is installed as packages. Client files and agents are merely copied to /usr/openv.
If Enterprise Client in your situation means SAN Media Server, it means that NBU Server software is installed. If Enterprise Client is used for Snapshot Client only, chances are that Client software is installed with agent and option software added via file copy.
Extract from install guide:
For Solaris
servers only, remove the 6.x versions of all add-on products and database agents.
The installation script displays a list of the add-on products and the agents that are currently installed. The script also offers to remove these earlier versions for you and Symantec recommends this method.
You also have the option to remove these items manually before the upgrade occurs. These items must be removed before you upgrade to version 7.0. If you remove these items after an upgrade to version 7.0, part of the NetBackup installation is destroyed and the product cannot function.
If you decide to remove these products manually, you must stop the upgrade here. Refer to the appropriate NetBackup 6.x documentation for instructions on how to remove each add-on product or agent.
So, the easiest is to start the installation and watch the output carefully.