I'm making progress, but I'm not out of the woods yet.
I've found that the 1.1, 1.2 (DXi supporting) reg keys are in...
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Cakewalk Music Software\
Dimension Pro The newer 1.5 keys are in...
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Cakewalk Music Software\
dp Which seems to mean that you can specify wav and flac multisample directory paths independently. That seems to work.
What
isn't working now is installing 64 bit DimPro 1.5.
I've installed DimPro 1.0 DXi and VSTi and updated to 1.2 (which has no 64 bit support...right?), AND installed DimPro 1.5 32 bit. That all works. The DXi version properly sees my wav multisample path and the 1.5 VSTi properly loads flacs.
The problem comes when I attempt to install 1.5 64 bit. The installer claims that I don't have DimPro 1.2 installed.
The question is, what all is the installer using to detect a good 1.2 installation? What could be confusing it? Is it finding vestiges of 1.5 or 1.5.5.16 laying around? I realize that this is the kind of thing that companies like to keep secret (and for good reason), but DimPro is now being given away AND has been deprecated by Rapture Pro. So, I'd think letting the cat out of the bag wouldn't cost them anything.