look into Netscape 6.0, i believe it has a way to retrieve mail from aol....otherwise with OE your out of luck.
maybe you can forward all of his aol mail to his new email address, as long as his account is still active, if account is dead, email is gone....other than that i dunno, with aol your very limited....keep in mind aol mail is not stored on his computer, it's kept on aol mail server....reason # 139 why i think aol sux.