Press [CTRL] + [SHIFT] + [C], when you hear a sound, 
enter the desired cheat.

Code            Result
-----------------------
gold           - Max Gold.
mana           - Max Mana.
explore        - Reveal Map.
fog            - Disable Fog.
research       - Research All Spells.
win            - Win Scenario.
lose           - Lose Scenario.
freemove       - Free Movement.
towns          - View All Towns.
spells         - Free Spells.
instantprod    - Instant Production.
instantres     - Instant Research.
ai             - Toggle AI.
upgradehero    - Upgrade Hero.
cityspy        - Spy on Enemy Cities.
emergehero     - Summon hero spell.
instantgro     - Toggle observation.