I was in search for the software myself after buying a ct600.1 off ebay. I had to do some hunting, but was able to get the software from the company that bought the remains of the old B&K company. I uploaded it to Google drive and sharing here so anyone that needs it doesn't have to struggle to find it. Note, I haven't installed it yet, so let me know if you're successful w/ it.

[Link: drive.google.com]