Once you resolve the "please enter your activation key 7554" problem, take these steps to avoid a repeat:

was originally released with a digital rights management (DRM) system that requires a unique license key for activation after installation. This process is common for physical DVD copies or original digital downloads from the developer's site : 7554: Dien Bien Phu (Video Game) : Emobi Games (now Hiker Games) Release Date : December 16, 2011 (Vietnam) How to Activate Launch the Game : After installation, run the game's executable. Activation Prompt