What happened eventually is that I gave up and got a new but less fancy card - the installation of which caused Vista to go and find a new driver, which also works with the old card! I could not get Vista to go look for a driver for the old card on its own. But I've reinstalled the old card and it works (though I've since run a benchmark program and discover it's well below par in performance. That may not be new since the new driver.)
I appreciate the speedy answers