First of all download and install cheat engine
http://www.cheatengine.org/downloads.php
Start the darkness 2 demo and play it through until you get to the game proper (the part where you're walking around with those daemonic tentacles hanging out of your ears)
windows key or alt-tab out back to the desktop and run cheat engine
click this button at the top left (just under the "file" dropdown menu)
choose the darknessii.exe process and open it
from the "value type" drop down menu, choose "Array of bytes"
and paste this value into the box
8C 42 00 00 00 00 00 00 00 00 00 00 34 42 01 00 01
and click the "first scan" button
Select both the lines in the window on the left there by clicking on one, holding shift and clicking the other.
Then click the red arrow pointing to the bottom right corner there
Now in the bottom window, select both lines by clicking one, holding shift and clicking the other, and then press enter.
The fov is vertical and the default fov is 45, to change it to 68 (100 horizontal), change the "34" to "88" and click OK
So cheatengine should now look like this
go back into the darkness 2 and it should now look like this, you should actually see the fov widen as you start to play.
I don't know what FOV you all prefer, I only have one 16:9 monitor so I always go with a horizontal fov of 100. I'll put some values here but if you have any you want specifically just ask :D
Just change the "34 42" that we changed to 88 42, to the following value instead to get the different fov.
The games fov is vertical but I'm using horizontal just to save you working it out.
90 = 6C 42
120 = B2 42
150 = 02 43
170 = 23 43 (This looks as if it's as high as it goes)
To clarify, to get an horizontal fov of 150, the value would change from
8C 42 00 00 00 00 00 00 00 00 00 00 34 42 01 00 01
to
8C 42 00 00 00 00 00 00 00 00 00 00 02 43 01 00 01
Hope that wasn't too long winded. I'm sure you'd rather go through that than playing with the claustrophobic, restrictive, eye-spinning, nausea and headache inducing console style narrow fov from hell.
The reason I can't make a nice easy to use program like I did with EDF is because the game chooses a memory address at random every time it starts, it may even choose a new address at the start of each level so you'd have to minimize out and change the fov each time. Nightmare, if only devs knew what they were doing when it came to the pc platform. Hopefully if enough people badger them, they'll add a slider in the full game. I very very much doubt it though.