When you upgrade or otherwise replace your Nokia phone, the only way to move your N-Gage games over is to buy them again. From All About N-Gage:
"To combat piracy, the activation code is linked to just one phone. It does this by checking that phone's unique IMEI number (every phone in the world has its own), so if you try to use the same activation code on another phone it won't work.The problems start when you try to upgrade to a new phone. Because it will have a different IMEI number, you cannot use your existing game activation codes on it ... if you sell your old phone, or if it breaks while out of guarantee, you lose your games forever."
When you buy into DRM, you get everything you deserve when the vendor shafts you.
What's most amazing about this is how it punishes Nokia's hardest-core fans, those who buy its top-end handsets and who frequently upgrade. They pulled the N-Gage brand out the toilet for this? The more one tries to understand the corporate psychology behind it, the more inexplicable it gets.