Post cup noodling around doing not much at all and decided to download the trial version of Parallels Workstation for Debian Linux. After some aptitude fixing packages that were not installed; finally managed to get Parallels booting.
Next step: attempt to get the X11 appearing from the client application (installed on the Debian server) to the display server on my Mac.
Something with the video is hosed; and it’s possible that Vista won’t work over the X11 connection.
Anyway, that killed some bits on the Bigpond and a couple of hours.