[CentOS] Launching X-Windows at different runelvels

Hi all,

  I need to launch X-Windows at runlevel 4 and 5. CentOS only start up x-windows 
at runlevel by default. I have modified /etc/inittab to accomplish this:

x:4:respawn:/etc/X11/prefdm -nodaemon
x:5:respawn:/etc/X11/prefdm -nodaemon

  But this returns errors every time that start and stop system ... Which is the 
correct form to launch x-windows under centos at different runlevels??

Many thanks.

-- 
CL Martinez
carlopmart {at} gmail {d0t} com