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 - Unknown Effect