I don't believe it was ever available for download. Just the disks you purchased when you bought the software (as Kev mentioned).
There is a newer version for sonar (Sonar home studio) for 50 USA dollars.
https://www.cakewalk.com/Products/SONAR-Home-Studio The newer version is really the way to go. Sonar 6 running on newer Operating systems isn't going to create a formula for success.
PS- Please turn your caps off (it appears as if you are yelling).