Most probably, the password field is grayed because an offline account is selected in the field above. Offline accounts don't have passwords in BF2.
It's safe to play in singleplayer with an offline account, but if you want to play in multiplayer online, select an online account in the launcher.
If you don't have an online account, launch the game with that offline account you have now and you'll get the vanilla BF2 form for managing accounts.
