Well, I thought I should update, since it's been several days...
I've been going back and forth with the techies at NCSoft (the company that makes Guild Wars), running a program called AquaMark3 at their request, and the conclusion is that I need a new video card, there is something wrong with the old one. Perhaps this was getting ready to happen, and the driver changes pushed it over the edge? It's an integrated video card, which means it was eating up memory anyway.
That's the bad news. The good news is that a friend says he's going to send me a dedicated video card, which I can install in the AGP slot in my system. So while I'm waiting for it to arrive, I'm going to learn all I can before attempting this. I don't want any more botched jobs on my part.
My thanks, again, for everyone's help with this. I'll be sending friends to this site when they need help.
Tanith