I downloaded BC42 the other day (wow it's been a long time!) so I could load it up and add a load of vehicles, get the coordinates and edit my patches/con files.
Now from what I recall, if for example I wanted to load El Alamein in DC_Final, I would load it in bf1942 first to load all the necessary files; heightmap etc and then open the DC_Final version.
I got this working to begin with, but now it just loads mostly a plain colour with not textures, vehicles or buildings...
Am running Win7 64

I have tried running as compatibility Win XP and running as administrator.
I think this is a known issue? I saw a vaguely related post from a couple of years ago.