Hunting down a used DVD copy for PC is still a viable route, as these include the printed 20-character serial key.
Finding a working serial key for Need for Speed: Shift 2 Unleashed serial key for nfs shift 2 unleashed
If you already own the game digitally but cannot find your key: Hunting down a used DVD copy for PC
Are you having trouble activating a physical copy of the game, or serial key for nfs shift 2 unleashed
Shift 2: Unleashed — "Activation limit for serial number exceeded".