Make sure you do a full uninstall, then check the following. Open regedit and check for X3 keys under
HKEY_LOCAL_MACHINE\SOFTWARE\Cakewalk Music Software\SONAR Producer
HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer
delete the X3 keys there.
Then check... and delete Sonar X3 directories if they exist.
C:\Program Files\Cakewalk or C:\Program Files (x86)\Cakewalk
%ProgramData%. Navigate to ...\Cakewalk
%AppData%. Navigate to ...\Cakewalk
HTH