I just had to reinstall the software so I could use the receiver to do telemetry. I put it on Windows 7 X64 and I think it mentioned something about the cable. I no longer know where the cable that came with it was, but I thought I recalled you can use any Mini USB cable. So I gave it a try and the software was able to communicate with the R20 with no problem. So it would appear the native windows drivers and a standard USB Mini will work fine, there is no requirement for proprietary cables such as those from RT Systems that use an FTDI Chip and unique PID and VID values.
It's easy to find your port number. Plug the cable into the computer, then the R20. Open Device Manager, and expand the "Ports (COM & LPT)" section. Now turn on the R20. You will see the window refresh, and now you will see a new entry that says "USB Serial Port (COMxx)" where 'xx' is the COM Port that the R20 is now using. Set that port in your CS-20 software, and they will now communicate.