See what I want to say is that you wouldn't be able to check the status of something(xinetd) which is not at all installed. xinetd needs to be installed first...
You can try the following command
"yum install xinetd".
If the above command doesn't works then insert your centos DVD and find the package named something like xinetd-**.rpm. And you should be able to use the command
"rpm -ivh xinetd-**.rpm" while being in that directory.
You can then use your xinet commands.
You can then refer to the following links to configure xinetd.
That might help you...