Well first you enter the game files (where'ever you have placed them), the folder you're looking for is called
IL-2 Sturmovik 1946 and should be within eithr the folder
Ubisoft or
Ubi soft (Note the space between Ubi soft).
Anyway when you open the folder
IL-2 Sturmovik 1946 you will amongst alot of other folders see one named
Conf, open it. When you've opened it you will see a long list with a lot of subtitles, look under [Windowed] and change the resolution to 1680x1050 there.
It looks like this to begin with:
[window]
width=1280
height=1024
ColourBits=32
DepthBits=24
StencilBits=8
ChangeScreenRes=1
FullScreen=1
DrawIfNotFocused=0
EnableResize=0
EnableClose=1
SaveAspect=0
Use3Renders=0
You need to change it to:
[window]
width=1680
height=1050
ColourBits=32
DepthBits=24
StencilBits=8
ChangeScreenRes=1
FullScreen=1
DrawIfNotFocused=0
EnableResize=0
EnableClose=1
SaveAspect=0
Use3Renders=0
Note that I just changed the resolution from 1280x1024 to 1680x1050.
Now that this has been done try to opne the game, you will note the cropped picture. Now do not enter any video settings inside the game, it wont do anything but change it back to 1280x1024, so just leave that alone and you should be ready to play.
I have a 20" Widescreen Samsung monitor and it works for me, but the actual picture will be 4:3.
Good luck KK, I hope that helped