It's in the registry, look in HKEY_CURRENT_USER/Software/G5 Software/T34.
There's USSRCampaign and GerCampaign, the stock value for these keys is 1, if you put 6 it unlocks the whole campaign.
If you have XP, just click start->run, and type "regedit". I have no idea how to access it with Vista though but google is here to help
