Did you simply press the enter key and see if it ask for a password again? If your set it up as a user and don't create a password, there is no password to enter. You can boot the CD up and look at the help files. Those files may tell you what you need to enter for a password. CentOS is Red Hat based, if I remember correctly, but I could be wrong.
If you have the bot screen for recovery, when it boot and goes through the screen, it ends up in bash and you use this for the terminal. Centos commands for passwords is;
passwd – Passwd is used to update a user’s authentication token(s). Passwd is configured to work through the Linux-PAM API. Essentially, it initializes itself as a “passwd” service with Linux-PAM and utilizes configured password modules to authenticate and then update a user’s password..
example: user1@foo ]$ passwd newuser (this command prompts the issuer to provide a new password for the given user and then updates the password database accordingly replacing the previous password with the new one.)
If you don't quite understand this, it is a lot easier to reinstall the Linux or Unix and make sure you create a user name and a password for that user. Most Linux or Unix distributions disable the direct access to the root account and use the SUDO command to give a user temporary access to the root account. Only root can change the operating system.