I have files missing when I use DP 1.5  in Sonar X-1 64 bit. They are not missing when I use Sonar 8.5 32bit.
 
When I say files missing I get a error box and an open text file telling me that samples/files are missing or corrupt or not installed correctly.
 
So where do they default to?

The multisample files (sfz) are stored at

C:\Program Files\Cakewalk\Dimension Pro\Multisamples

The program (prog) files that you actually see while selecting sounds, are stored at

C:\ProgramData\Cakewalk\Dimension Pro\Programs

ProgramData is a hidden folder by default.