I just realized that WIA wasn't installed on my new computer.
After a moment of panic when I couldn't find the disk (who uses them anymore ?), I managed to get the game installed, then patched, and then quickfixed (I notice that the quick fix is still in beta after all these years).
Reflecting on my moment of panic, I decided to check and see if I had ever registered the game with Matrix, and of course I hadn't. My copy doesn't even mention Paradox, so it may be a bit antediluvian.
I fed my very long serial number into the Matrix website, and not surprisingly it didn't recognize it.
Should I wait until September (in which case I may forget to do anything about it)?
I have this nagging feeling that the next time I try to install on a new computer (several years from now, knock on wood) I may not be able to lay hands on the disk, if computers are even still using them by then (don't laugh -- I found some floppies in the back of my closet the other day). So thinking ahead, it would probably be a good idea to get registered to protect against a change in technology.
In the meantime the game seems to be working, though I'll have to remember how to restart my old computer to figure out what mods I had installed in it (King Philip's War looks great, by the way).