Well, Trotter, you called it, albeit indirectly. You wrote "... hard drives are magnetic media..."
I had a penny-sized (but thicker) magnet on a counter, and it somehow got from there onto the outside of my computer box.
I wasn't able to run System Restore from Windows disks, because I only have backups, not the actual Windows XP disks. That was moving outside my comfort zone anyway. Didn't use Driver Sweep either, since it now looks like the driver wasn't the problem.
I'll start a new thread in another forum. I need to know how to figure out what-all is wrong (is the graphics card going to need replacing? Are the Restore points corrupted or is the System Restore application itself the problem? What else is wrong that I haven't discovered yet?) and then how to repair it.
Thanks to all who posted, and please feel free to answer here or in the new thread I start if you have any ideas about what diagnostics I can run without buying a package. (I've been unemployed a looong time, can't afford this!)