Hi, i made custom installer too for this game and encountered the same as holyjoker. Cannot find which registry or file need changing, even with process monitor. Luckily found this one:
http://www.mediafire.com/?05gjghhllw1waa5
It's like mini installer, if you installed the game using custom installer, run it with custom installation, point to installed LA Noire dir, uncheck all of 3 items, finish installation. Enjoy
