i did something like this a year or two ago, maybe from the same website
http://www.widescreengaming.net/wiki/Doom_3
but the problem i had was that the game would reset itself everytime i started it. so i was hoping someone had already made a patch to just have it normal.
the problem is that my desktop monitor always stretches non-widescreen stuff, and i have to change that manually with the montiro's menu settings, its not something i can do by going to the graphic cards settings. its crap like that.
just thought someone here might have known though. :)