install kde4

1.install require package for x windows
#yum groupinstall "Desktop" "Desktop Platform" "X Window System" "Fonts"

2.install kde desktop
#yum groupinstall "KDE Desktop"

3.modify /etc/sysconfig/desktop if this file doesn't exist, please create it and add the contents as below
#touch /etc/sysconfig/desktop
#vim /etc/sysconfig/desktop

DESKTOP= "KDE"
DISPLAYMANAGER= "KDE"

4.Reboot the machine
#reboot