Place the following line as the last line in the "hardline.cfg" file.
 Type it exactly as shown or it won't work (note case sensitivity and
 spaces): 
 
 CHEATING IS SOMETIMES USEFUL BUT FOR HOW LONG ???
 
 When enabled, the following are the cheat keys:
 
 Cheats - Results:
 
 X - invincible
 BACKSPACE - kill all enemies on screen
 INSERT - full health
 PAGE UP - adds accessory weapon ammo
 HOME - adds main weapon ammo