For windows, click the start button and type

%APPDATA%

This opens that folder, then find folder "moi"

FYI: I keep my ini file in MoI's root installation folder. It will look there first, and keeps it more handy for the guy who wants it more often...

Michael also put a button for "edit ini" in the options panel, which finds and opens it for you. Havent tested that with the new beta yet though