I can encrypt a cd so it cant be read without a passowrd.... unfortunately, it cant be read WITH a password either.... On a more serious note, unless you want to get into military grade encryption, you're outta luck.
Several programs can encrypt the data on a cd so that it is unreadable without a password key, Pretty Good Privacy comes to mind. I have heard of others that encrypt the entire cd - EncryptX, CD-Protector, but they are not free.