AD2 came with my upgrade to Sonar Platinum. I've opened it up in Sonar, and all the modules must be purchased. So, not much of a deal if one has to spend $90 for each kit. I would assume that pasting that registration code somewhere would unlock them, but I can't find anywhere to register within the software.

Rice, you first have to set up an account at XLN Audio, and after logging into your account, you can use the registration code.
 
You will then also have to install XLN Audio's Installer on your PC: http://www.xlnaudio.com/support  
 
Once you do both of those steps and then run the installer, your registered products will show up and will likely get updated immediately.
 
Your midipacks won't be shown in the installer, but will be seen inside the actual AD2 application.  
 
(BTW, you don't need to spend another $90 to get this bundle to work.........it's probably saying that since you haven't registered any of your products yet).
 

I did all that, so...
 
I went to XLN's site and finally found the registration stuff. So when I fire up their installer, they give me three "deals," which are installing now. Three kits, 3 MIDI paks, and 3 kit pieces. The rest cost $$. The process is not too user-friendly.
 
It's almost frightening at how large these files are and how everything (Sonar, AD2, Native Instruments, etc.) gets installed on my system drive, which really ticks me off. Glad I bought that 4 TB external backup drive.
 
EDIT: I see that in the XLN installer, under 'Advanced,' they have an option to move everything to a different drive. Now that's what I'm talking about!

Ricebug
 
EDIT: I see that in the XLN installer, under 'Advanced,' they have an option to move everything to a different drive. Now that's what I'm talking about!

Yes, I moved it to my 3TB samples drive. Even all the Native Instruments stuff is on my 3TB drive..........I only keep my OS, software, VST's etc...on my C: (system) Drive.
Although all of Sonar Platinum is also on my my C: drive, I'm sure they'll give an option (if there's not one already) in one of the updates to relocate the samples/loops stuff to another drive.