changing battlefield 2 v1.5 cd-key

open regedit
navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Electronic Arts\EA Games\Battlefield 2\ergc
change the data of (Default) string to the format as below
x93921111-2222-3333-4444-5555
x9392 is the leading string , and 1111-2222-3333-4444-5555 is your cd-key

in the version before 1.5? x9392 is not needed