In a PDF I found on this site it refers to some registry deletions that don't make sense (to me).
If the purpose of the pdf called "SONAR 2015 Clean Install Instructions" is to completely eradicate Sonar and start over why this:
Delete the following Registry keys: If you do not have one of the Registry keys below, simply proceed to the next one on the list.
HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR\<Platinum/Professional/Artist>
HKEY_LOCAL_MACHINE\Software\Cakewalk Music Software\SONAR\<Platinum/Professional/Artist>
HKEY_LOCAL_MACHINE\Software\Wow6432Node\Cakewalk Music Software\SONAR\<Platinum/Professional/Artist>
Why not delete the whole tree?
(I have to remove 8.53 and Splat. So, I would imagine everything Cakewalk related )
ie:
HKEY_CURRENT_USER\Software\Cakewalk Music Software
HKEY_LOCAL_MACHINE\Software\Cakewalk Music Software
HKEY_LOCAL_MACHINE\Software\Wow6432Node\Cakewalk Music Software
Thanks