i ve read so many post on it but cant even type root
after boot up it will display this

centos release 5.2(final)
kernel 2.6.18-92.e15 on an i686
init : Id "x" respawning too fast:disabled for 5 minutes

if i press ctl+alt+f3
it will bring linux login
and when i type root it will say
"can't login incorrect login"
and its the right login
can you help me please

I do not know what's exactly wrong but sounds like your having problems with the X GUI, you could boot into single user mode, and change /etc/inittab id:5:initdefault: to id:3:initdefault: which should boot you up into console and not load X. If it's not 5 then that'd be a potential cause too as 5 should be the init runlevel for using a GUI interface. Unfortantly I can not be too helpful on this one as I don't use X much in Linux and never seen this problem occur before but atleast if you change down to init run level 3 you should be able to check out settings and such.