I install manually (as opposed to through the CCC).
 
Like all the manual installs, I downloaded the Rapture Session installer and the five or so other downloaders, for like Atmospheric, Guitars, Keyboards etc.  When installing Rapture Session I was offered the choose your custom path to install.  Great!  I installed Rapture Session on my desired drive.
 
When I run Rapture Session Platinum (Kingston) it says I'm in demo mode.  I have a serial number for it.  I don't see a way to activate it.  From what I'm investigating so far, it seems the only way to activate it is to use the Command Center to install it, in which case it would get installed on my C drive, where I don't want it.
 
Does anyone know how to activate Rapture Session without using Command Center to install it on the C drive?  I have it installed in my desired drive, I just don't see a place to activate.
 
Thanks!

If you click the cog/gear icon in the upper right of the window, then the Paths tab, you can designate any location for the Cakewalk content. 

Upon clicking the cog on the upper right next to the title "RAPTURE SESSIONS" the is no Paths tab.  It only says:
 
Open user guide
Enable logging
Assign MIDI CC to Previous Program...
Assign MIDI CC to NEXT Program...
Upgrade to Rapture Pro
 
I advise against paying for an upgrade as similar path issues will be experienced. 
 

Open ccc. When it displays your products, click the gear in the upper right… 

I can't remember where the setting is but you're looking for Verbose mode/installation.

That runs the installer offering various options including where you want to install the files you want.

Alternatively you can definitely do it by navigating to the location of the download file for your program and double click the file to run it. That is verbose mode and you will get the option where to instal your files.

Check CCC on the options page (Gear icon) for the location of your installation files.