Sorry I didn't say that I was using KDE. I didn't know it would make a difference.
KDE is different to what you describe. The Configure Hardware and Monitor Display just gives a list of what seems to be types of video card, or something. Mine is locked on to 'Vesa'. Anyway, I tried right clicking it and, low and behold, I was then able to configure the card to what I wanted, and had before I re-installed.
Many, many thanks for your input.