Which seems to work nicely with the in-built driver options that Win10 provides. So, after much frustrating effort, including managing to get one of the adapters to sort-of work with an old driver, I bit the bullet and bought a new adapter, one of these:

I had 2 of these lying around that I spent much time & effort on, unsuccessfully – mostly due to hardware in the adapters that was too old to have any drivers that would run on Windows 10. The mill has been gathering dust since we moved to Scotland in 2014 and I have only recently been resurrecting the PC side – the original laptop that I used had a serial (COM) port, which is long gone from modern spec PCs, so a major hurdle was to find a suitable USB-to-serial adapter that would do the job. I converted my Taig CNC mill some years ago to make use of DeskCNC as the controller software/hardware (writeups were in MEW at the time).