Go to the game folder and you'll find game.exe file in the "bin" subfolder. Right click on it and select "Send to > Desktop (create shortcut)" to make a desktop shortcut. Now, right click on that shortcut on your desktop, select properties and a new screen should pop up. Add the " -cheater" parameter (without the quotes) at the end of the target field so it looks similar to this:
"C:\Program Files\THIEF\Hired Guns\bin\game.exe" -cheater
Also, make sure that the "Start In" field points to the main game directory, ie:
"C:\Program Files\THIEF\Hired Guns"
Click "Apply" to save the changes and run the game using that shortcut. Press [~] while playing to bring down the console and enter your codes:
cheater <on/off> - Enable/disable cheating.
showall <on/off> - Unknown.
finish <win/lose> - Unknown.
grave - Close the console.
exit - Quit the game.
heal <person> [points] - Sets the health points of the mercenary specified.
gainxp <person> [experience] - Gives experience points to the mercenary specified.
setPersonHealth <person> <points> - Sets the health points of the mercenary specified.
kill <person> - Kills the specified person.
gameStage <#> - Unknown.