First of all, you will need to download FOV Changer for Aliens vs. Predator (2010)
You can get it here[github.com] *

Unpack it anywhere, go to bin directory and launch AVP2010_FOVChanger.exe

If everything works, you will encounter this screen:

1. Status (it will say AwP is running when it detects game running)
   
2. Displays current FoV of running game (default for Marine and Predator campaings ~ 60)
   
3. Insert desired horizontal FoV here (I recommend 90)
   
4. Click this checkbox to set hotkey for changes to take effect in-game
   
5. Select the version of the game that you are running

*If the link doesn't work, try downloading it from here https://github.com/SuiMachine/AVP--2010--FOV-Changer:

Now with interface out of the way, here's what you need to do to get it to work:

1. Run the game
   
2. Load into the game (continue or start a new campaing)
   
3. Alt-tab and launch AVP2010_FOVChanger.exe
   
4. Enter desired FoV (don't forget to select correct renderer first, though! If status bar doesn't say AvP is running, you are doing something wrong.)
   
5. Set hotkey for FoV change (I use substract) - This step is highly recommended because the game has a tendency to discard FoV changes every time it loads a save, new level or plays a cutscene.
   
6. Alt-tab back into the game and hit the designated hotkey for changes to take effect (you have to exit the menu first, though)
   
7. Enjoy not having a headache from tunnel vision!

I did not create the tool in question, all credit goes to SuiMachine[github.com].