I had the same problem and asked for tech support from Sony: they of course said the net MD wasn't designed to upload your own recordings to computer - which was really what I had bought it for!!
But this is what their man said, which I think agrees with above advice:
"Provided your computer has a LINE INPUT, this can be done in an analogue fashion, by connecting a cable between the headphone sockets on the MiniDisk and the LINE INPUT on your computer. The cable required is dependent on what is used on the computer, but generally it would be a mini-jack to mini-jack".
Haven't tried it yet: watch this space!
TB