Try booting the Install media and entering 'linux rescue'. Strictly speaking, that works on the std Centos/RHEL media; not sure if it will work for you.
If it does, you need to mount the HDD and edit /etc/inittab and set the initdefault line
#Change the 5 to 3
when you reboot, it should just bring up the console without X-win. Login as root and try
& see Chap 30 http://www.linuxtopia.org/online_boo...ion/index.html