Usually found on the back of the game manual or provided in your billing information if purchased digitally. It follows the format: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX Unlock Request Code:
A final code provided by Konami’s servers to "bind" that serial key to your specific computer. pes 2011 serial unlock request code
Sometimes the game "forgets" it is activated. Advanced users occasionally use registry files to manually inject the serial key into the Windows Registry at HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\KONAMI\PES2011 . Usually found on the back of the game