CentOS black screen on boot

1. Hit any key at the grub screen.
2. Enter 'e' to edit boot selection.
3. Highlight the kernel line, and enter 'e' again.
4. Add a space and an 's' on the end of the line.
5. Hit enter followed by a 'b' to boot.
If this still locks up, try again, but at step 4, remove the rhgb and quiet options before adding the s.
6. Edit /etc/inittab. Change the id:5:initdefault: to id:3:initdefault:

Reboot.

Now your system starts with X turned off.
You can run troubleshoot X.

Credit to: http://www.centos.org