ISSUE : Message Displays' While upgrading From BE 2012 SP4 to BE 15
MESSAGE : Deduplication Option is no longer licensed in this upgrade. You may not remove the license during the upgrade. To continue, either add a serial number for Deduplication Option, upgrade as trial, or remove the option in the previous version, then continue the upgrade
Solution: Open regedit, navigate to: HKLM\SOFTWARE\Symantec\...
Delete the \Puredisk\ registry key and it's child \Puredisk\Agent\.
If you have never installed, trialed, used or licensed dedupe at all these keys will be completely empty of values
Quit and re-run the Installation. The wizard should continue past this point and straight to the options screen. This should allow you to install/upgrade BE 15 with licenses the first time, without having to go through the trial install first.
You are good to go
...you should be adding this in as a Blog: