Installing EPEL repo in CentOS is simple, if you do not know what EPEL is, read more about it here.
rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm
To configure epel or disable it use
nano /etc/yum.repos.d/epel.repo
and then switch the config enabled to 0 (or vice versa)
Don’t forget to do the following
yum clean all