The computer came up with only one monitor on, rather than both as usual, and that one monitor was in 800x600 resolution.
I sighed at this, went to the display control panel to fix it, and discovered that the tabs specific to the display adaptor were all in French. Luckily, I could puzzle out most of them from context and vague leftovers from the French class I took a decade ago.
However, as best I could determine, there was no way to get things back to a state of having the two monitors show up independently, such that I could put different resolutions on them and put the secondary monitor on the left of my primary monitor.
So, I spent about an hour trying to uninstall the new drivers, and reinstalling the old drivers from CD (which was luckily handy), and fixing things. It turns out that the ability to have two independent monitors, much like the language settings, needs to be set when the driver is installed.
And, since Windows of course rearranges all one's icons permanently when one temporarily downsizes to a lower resolution, all my desktop icons are still in disarray.
I am Very Displeased with this.