This synth was included with the X1 Production Suite which I originally bought. I uninstalled X1 at some point after installing X2 and had no problems with Z3TA+2.  Recently however after following Cake's online steps to do a clean uninstall (deleting registry keys etc), the synth is now asking for a registration code. I can provide it, but the problem is that it doesn't "take," i.e. the registration dialog pops up every time I open a new instance of it. I've tried running in standalone as administrator but that doesn't help either. I've also tried disabling antivirus etc. 
 
Support hasn't been able to rectify the problem yet...last I heard from them, they asked me whether I'd run any registry cleans recently. I'm thinking that my deletion of X1 registry keys has been to blame and thinking about reinstalling X1. However, I'd like to know: will reinstalling X1 screw with my installations of X2 or X3 at all, with regard to any of the shared utilities? 

If I'm not mistaken I think  you will need to do a basic install of X3 afterwards.  Perhaps even just reinstall the X3C patch.  I recall reading somewhere that certain shared files get overwritten when you install older version of X series.  This is all based on an incomplete memory so you may want to get that confirmed.

Z3ta+2 was not a separate install during your X1 install?
 

dubdisciple
Z3ta+2 was not a separate install during your X1 install?
 

Yeah I actually tried reinstalling it alone from my X1 discs, but the problem still remained. I'm convinced it has something to do with the X1 keys I deleted. 

i wish I had something  for you.  I bought X1 and z3ta+2 separately.  You would think the production suite was simply seperate packages combined and that uninstalling one would not affect the other.  Maybe do a sweep for dupe files and make sure you don't have a partial install of z3ta+2 somewhere .  I had an issue like that with a Sonar plugin that turned out to be a conflict with a previous version still on my system.

or maybe try reinstalling from download of z3t+2 file instead of disc.
 

Never heard of anyone installing an older version of Sonar with newer versions of Sonar installed.
 
I didn't realize this but I still have X1 32b and 64b still on my machine!
 
Did Zeta +2 come with X1? I got it when it was on sale, so I don't remember if it was a freebie at one time.

Grem
Never heard of anyone installing an older version of Sonar with newer versions of Sonar installed.
 
I didn't realize this but I still have X1 32b and 64b still on my machine!
 
Did Zeta +2 come with X1? I got it when it was on sale, so I don't remember if it was a freebie at one time.

There are a number of reasons one might install an older version.  A common reason is a user discovers a plugin they used is no longer included with the newer version.
 
Z3ta+2 was part of a Production suite package Sonar offered for awhile but my impression was that is was more along the lines of pay one price and get Sonar X1 , Z3ta2 and whatever else was included as separate components and not part of one big install.  That is why it would seem odd that uninstalling X1 would cause his problem.