I have used hyperterminal on Win 7, so I know it works. I have found rtd explorer to be a bit buggy on Win7, but other users are reporting it works fine on win 7. Make sure you have hyper terminal set for 19200 baud 8-N-1. I am assuming you are using a serial to usb cable. Open device manager and see which com port it has been assigned to, it changes on mine just about every time I use it.
That's why I now use moserial on linux, a bit more friendly and stable than hyperterm on win7.