What is wrong if the xwindows says it can't start kdeinit?

There may be some errors posted in the /root/.xsession-errors file that might help to identify what the problem is.

make sure that /opt/kde/bin is in your PATH

temp solution
------------------
# PATH=$PATH:/opt/kde/bin
# export PATH

then run startkde

you will have to edit your profile to make it stick(ex. .bashrc, .cshrc, etc...)

Hope this helps.

If this error is a result of modifying/upgrading kde, I found that some notes from the kde site helped:

"I upgraded KDE and it seemed to go fine, but when I start it, I get a blank grey
screen, and nothing happens. There are errors in the console about DCOPserver.
What's going on?
KDE uses several temporary files during it's operation. These are usually to be
found in the following locations:
*

~/.DCOPserver-* (there are usually two of these, one is a symlink to the
other) *

~/.kde/socket-hostname
*

~/.kde/tmp-hostname which is normally a symlink to the next file:
*

/tmp/tmp-kde-USER
*

~/.kde/socket-hostname which is also normally a symlink to:
*

/tmp/ksocket-USER

If the symlinks get broken, usually because a cron or shutdown script is
emptying out the /tmp directory, then strange things will happen. These files,
and the symlinks, will all be created automatically at the start of KDE so you
can safely remove them while KDE is not running.If you are getting only a grey
screen when you start KDE, or if you get an error message telling you to Check
your installation, then shut down X and delete all the files listed above, then
try to restart X."

this worked for me, although I seem to remember that the files mentioned were not exactly in the path quoted, so you may have to look around a bit. On reboot it all came up again.