I was having the same problem (Dimension Pro warning, Rapture install never started) and tried the workaround. It worked for me. These tips might help:
1)
Check both your 64 bit and 32 bit registry entries. It turns out I had "Dimension Pro" for 32 bit and "Dimension", "Dimension LE", and "Dimension Pro" all for 64 bit. I had to rename all of them in order to get the installed to proceed past the Dimension Pro warning.
2) If for some reason you get the Dimension Pro warning, or need to abort the installation, you can save some time by immediately going to your windows temp directory, finding the Sonar X2 folder, and then
copying the unpacked setup files to a temporary location. Do this before the installer terminates, since it will clean itself up. If you copy the temporary setup files files, you can run the setup directly via setup.exe, and not have to run the unpacking installers.
3) Once the Rapture installer is done,
run the Rapture app standalone as administrator; this will let you enter your registration code