Does anyone know which file controls the monitor's refresh rate?

I was adjusting the monitor resolution, but accidentally adjusted the refresh rate to an unsupported value (which offers itself, as though its legit).

The monitor went black, then a notice glided around the screen saying the video mode is not supported. When I restart, the notice appears again.

The last time this happened was years ago, the day I bought the monitor, a Samsung 192N, and I ended up having to start the computer from the OS X disk and reinstalling everything.

This time, I can boot into OS 9, and I'm posting from it, so I should be able to trash the screwed up refresh-rate file, if I know which one it is.

I've been dragging various preferences (and preferences folders) out of their places and rebooting, but so far no luck, and I'm stuck running System 9.

Edit: I can open the plists, that are readable, at least, with BBEdit Lite and change them.

I installed Tiger into another partition and copied a bunch of display files over to the corrupted system but to no effect. What a pain.

Reloaded Tiger.