Cheats:

 On the hard disk there is a directory called HARDLINE.CFG in it is a
 file called SETUP.CFG, edit this file and add, as the last line

 CHEATING IS SOMETIMES USEFUL BUT FOR HOW LONG ???

 Then play the game as normal and press

 [Insert]    To increase health
 [Home]      To increase the ammo of the weapon you are using
 [PgUp]      To increase ammo of your accessory weapon
 [X]         To become invincible
 [Backspace] To kill all enemies on screen