I bought X3 a few years ago when it was on sale, updated to E, but have hardly ever used it.
Some issues with my old DAW have me looking into it more, possibly moving to this newer computer.
I have something called 'Melodyne Singletrack', which I think came with X3, but can't use it since I don't have the proper numbers. Melodyne is not listed under My Products, so no activation code there. Documentation reads that it's only available in Studio and Producer versions.
So, why do I have it if they won't let you use it? Those few of you who have heard me sing know I need it.

A license for Melodyne 2 Essential was bundled with X3 Studio and Producer. The base version of X3 may have included a demo version of Melodyne. I do not know for sure. Melodyne Singletrack is the installed name for Melodyne Essential, Assistant and Editor. The license determines whether Melodyne Singletrack has Esseential, Assistant or Editor features.

Thanks, scook.
That's a good selling tactic; I can see how bad my singing is but can't do anything about unless I buy the full version.
Or practice, practice, practice.

As far as I remember the Melodyne essential that came with X3 was a full version, but there were special instructions on how to activate it on Celemony site. I can check later on today as X3 is still on my test PC (which was once my production one years ago).