navigate to Battlefield 1942\Mods\bf1942\Settings and open up VideoDefault.con in notepad. Unlock your fps with this line:
renderer.lockfps [fps number]
and you can change your aspect ratio with this line:
renderer.fieldOfView [number to the desired ratio]
Change to suit your aspect ratio:
1 for standard 4:3 monitor.
1.33333 for 16:9
1.25 for 15:9
1.2 for 16:10
Make both con files "read only" in properties!
Be advised that the screen will look like This with high aspect ratio! There can be more and larger "holes" even in the sides at higher resolutions! You need to experiment with this by yourself, to find the best display!