Cheat Method
     Open  the "settings.ini" file from your game folder with Notepad.
Add  the  following  commands  where  "1"  is  activated  and  "0"  is
deactivated.

Example:
     Add  the  line  "instagib  =  1"  (without  the  quotes)  to  the
settings.ini file to enable God Mode in the game.

Other commands than can be added: 

oreOverride - Enable/Disable Gore 
HUD - Enable/Disable HUD 
smartbomb - ? 
weakThrax - ? 
audio - ? 
music - ? 
FMVmusic - ? 
showFMV - ? 
screenText - ? 
fullscreen - ?