>> My rationale being, having a real keyboard plugged in to it might help getting Windows to see a keyboard, which is what you want. I'm just guessing though.
Especially something so old it comes with a cable with serial adapters!
I have quite a few older controllers/keyboards like that around here somewhere too. And if I remember correctly, I had to have a keyboard connected too to make some of them work. But not all. I imagine it has to do with the type of encoder (if it even has it's own) in it.
Pessimist: Oh, this can't get any worse!
Optimist: Yes, it can!