Wherigo Unlock codes allow you to unlock the Cartridge - essentially marking it as complete. For this Geotool to work, you should download the Cartridge for a Pocket PC Device.
Each time a user downloads a cartridge its customised to THAT Wherigo account - the unlock code only works for that account. However you can still unlock any Cartridge by using the "Enter the Unlock Code for another user" option. The name of the user embedded in the Cartridge is included here.