Instructions
Open the Hitman games folder and navigate through the directory to find the file titled "hitmancontracts.ini." The directory where this file is stored should be C:\Program Files\Eidos\Hitman Contracts.
Add the following two lines to the end of the file:
ENABLECONSOLE 1
EnableCheats 1
Once this is done, save the changes and exit the file.
Start the game and during gameplay, press "Shift + Esc" to display the cheat menu.
Use the up and down arrows to navigate through the menu, and the left and right arrows to change the values of each mode.
A value of 1 will activate a cheat mode, whereas a value of 0 will deactivate the cheat mode.
For example, "God 1" enables God Mode, where as "God 0" disables God mode. "Invisible 1" makes you invisible to enemies, and "Invisible 0" deactivates the invisible mode.
Enter in-game cheats while playing the game, not in the console. These in-game cheats can be found at the Gamespot link in the resources below.