mettelus
In X2 (not X3), I had to contact CW customer service and they sent me this email:
 
Hello,
Thanks for contacting Cakewalk!
Please use the installation patch here: http://www.cakewalk.com/Support/kb/reader.aspx/2007013294
 
There was a "patch" required to get a registered copy of Rapture to run in X2 (notice I said X2... in X3 this was not needed).
 
Michael

I just tried the patch. Didn't work. Usually it works when you run it in Admin mode, even that is not working. There is some problem somewhere, I just can't pinpoint.

Here is another suggestion... Just go directly to the cakewalk store/website and My Account and just register Rapture, DimPro, etc. there instead of through the synth.  Ugh, this isn't really that difficult.
 
Also, about "run as administrator," right click on the icon and then click on Properties; go to the Compatibility tab and check the "Run this program as an administrator" box; you will never have to worry about it again.
 
Sorry, I just had to get that off my chest.
 
Kind regards,
 
Living Room Rocker

Thanks Living Room Locker but I am stuck at the next step. I have already registered DimPro and Rapture. I get an "Invalid registration" code when I input those reg codes in the plugin.
 
I am aware of "Run this program as an administrator" checkbox.

Ok, I fixed the DimPro registration issue. I have two DimPro 1.5 in my account. 1 from X1 and now another from X3. This time during installation I used the serial # from X1, subsequently used the respective reg code in the first run and voila, it worked.
I will try similar tactics now for Rapture. I think the problem is similar cause I have Rapture 1.0 in my account. May be there is a conflict when it checks for the serial/reg code combination with CW server.
 
EDIT: Rapture reg. problem fixed by installing Rapture 1.2.1 and then 1.2.2 patch from KB. It brought my DLL to version 1.2.2. Not sure if the 1.2.2 version in X3 has anything extra.