switchdesk -- Changing Desktop Environment in Linux

Changing Desktop Environment in Linux:
using switchdesk:
Step1: Login as "root" user.
Step2: use the command "switchdesk KDE" to change in KDE mode.
OR use the command "switchdesk GNOME" to change in GNOME mode.
If switchdesk command fails??
Install switchdesk rpm from CD/DVD. OR use the command "yum install switchdesk" to install it from internet.
Thats All.