I have enabled selinux using GUI tools, but i have getting same SELinux is disabled message.
What is the output of "rpm -qa | grep -i -e selinux" and "cat /proc/cmdline" ?? Are you using a CentOS supplied kernel, or your own kernel? I suppose you would try adding "selinux=1 enforcing=1" to the end of your kernel line in your grub.conf, although I've never needed to do that to get SELinux to activate.
Barry