Noflb didn't work, BUT
On the site I found with it, it also said GeForce4's would need 640 x 480 - a resolution I hadn't tried.
...And it worked! :Brain:
But I wouldn't have found it if you hadn't suggested the noflb, so thank you!
God I'm such a dumbass, it's always something really simple that I've overlooked because I think if something else doesn't work, that's not gonna work. *hits head on desk*