Some older games use Starforce DRM which is a copy protection tool. Please follow this instruction to activate Starforce games:
1) Log in to your GamersGate account, go to "My Games" section, download your game via GamersGate Downloader and install it on your PC.
2) Start the game by double clicking on the game's .exe file in the root folder or its desktop shortcut icon.
3) You'll be prompted to enter your activation code. Copy and paste the code to the activation field and click next.
You have just activated the game. Have fun!