The removal of leftover registry keys is a common 'gotcha' kind of thing, and also frequently trips up folks trying to do clean installs of Sonar, so don't feel bad.
The other common 'gotcha' with an installation of Dim Pro is that on first launch, to complete the registration process, you need to either launch Sonar with the explicit Run As Administrator, or you need to launch the stand-alone Dim Pro with the explicit Run As Administrator, or it will not properly detect the registration code.
Please note that Run As Administrator is not the same as having your User account in Windows set up to be an Administrator account. Right-click on either the Sonar launch icon, or the Dim Pro launch icon, and then click on Run As Administrator, and then you can properly complete the registration process.
Hope that helps,
Bob Bone