Take care, or you will be w/o any graphical i/f!
Here is what I did. Seems to work...
cp -rps /usr/X11R6 /usr/X11R6_3.3.5
cp -rps /etc/X11 /etc/X11_3.3.5
Now intall your 4.0.1 stuff. This seems to overwrite the necessary
files in /usr/X11R6 and /etc/X11, but leave some necessary custom
scripts if you have RH... Now things may/may not work. See elsewere for
the posting of my problems...
But, in any case, you can fall back to your old X version by
cp -rps /usr/X11R6 /usr/X11R6_4.0.1
cp -rps /etc/X11 /etc/X11_4.0.1
rm -rf /usr/X11R6
rm -rf /etc/X11
ln -s /usr/X11R6_3.3.5 /usr/X11R6
ln -s /etc/X11_4.0.1 /etc/X11
Now, you are free to try out 4.0.1 or 3.3.5 at will by moving the