To enable cheats in the game, use a text editor to edit the ".ini" file in the ""\documents and settings\all users\application data\ubisoft\tom clancy's splinter cell chaos theory\profiles\" folder. Create a backup copy of the file before doing anything and make sure you don't use the "default" profile! Bind one of the following codes to a function key as indicated, then press the selected key during gameplay to toggle the corresponding cheat function:

fly - Flight mode
ammo - Get ammunition
health - Get health
invisible - Invisible to NPCs
invincible - Invincibility
summon echeloningredient.ewallmine - Spawn wallmine
summon echeloningredient.eflashbang - Spawn flashbang
summon echeloningredient.efraggrenade - Spawn frag grenade
summon echeloningredient.esmokegrenade - Spawn smoke grenade
summon echeloningredient.estickycamera - Spawn sticky camera
summon echeloningredient.estickyshocker - Spawn sticky shocker
summon echeloningredient.eringairfoilround - Spawn airfoil round

For example, if you make the following changes to the file, you'll be able to use [F2], [F3] and [F4] keys while playing for invisibility, invincibility and getting ammo:

F2=invisible
F3=invincible
F4=ammo