Link to better instructions.

Alter game files at your own risk and always make backups!

1. Create a file named debugconf.scr then copy the following lines into it:
!include("DebugConf.def"

NoLogos()
Cheats()
UseDeveloperKeys()
LoadCheatMenuParamsOnLevelStart()

2. Save the file "debugconf.scr".

3. Copy the "debugconf.scr" file to the [GameDir]\DATA directory.

4. Play the game, press [ESC] to enter the menu options & select "Dev Menu"

5. The following cheat options are now available:
* AI Nicks
* God Mode
* Cheat Mode
* Magic Ammo
* charge full
* Restore health
* Give Ammo
* Give Rifle
* Give Grenades
* Kill Active Enemies

[Edited by GT500, 3/26/2011 3:40:03 PM]

Did you follow the instructions at the link below?

Link