Ok, so I bought Hegemony during the steam sale. Started playing, spent about 5 hours on it at which point I exit the game to do other stuff.

Previously the bottom of the startup menu said it was a registered copy, no problems. Then after (for some stupid reason I can't remember) I click Register and then ok (Serial Number was input already). Now, this "Unregistered copy" message appears every time and the game only starts in demo mode.

Reinputting the correct Steam cd key results in a "Thank you for registering Hegemony: Philip of Macedon!" message but still only demo version.

What gives? Why have that register button there if all it does is un-register your game? :S

Does anyone know how to resolve this issue?

Thanks in advance, Revolve.

The reason this happens is when you install the steam version of the game it is already registered. There is a bug where if you register it again, the game will "unregister".

To fix this run Regedit
Go to start and in search or if you have XP click Run - Type Regedit

When regedit opens, navigate to the following folder:

HKEY_CURRENT_MACHINE\SOFTWARE\Longbow Digital Arts\Hegemony Philip of Macedon

(If you don't see that folder, you can right-click on the parent folder and choose New->Key to create it.)

You will see on the right side of the window Serial click that and hit delete on your keyboard. (This makes the game forget you even registered it in the first place)

Now click Edit - New - String Call it Serial and type in your CD-key given by steam and that will fix your problem.

Awesome that fixed it, thank you very much :)