Yep...The aud.ini file is the file which stores all the audio configuration infos.
it's located in
C:\Users\XXXXXXXXX\AppData\Roaming\Cakewalk\SONAR X3 Producer
You can access it in sonar using advanced mode in preferences,audio section (4th subsection)
When you install X3 over a previous install, it will import previous config files. It may be good to delete(rename to keep backup) it to have X3 rebuild it and be "Full X3"