I am not very familiar with Linux. May be I can find here an answer of one of my questions.
I want to install KDE for some tasks, so it may be easier to work in KDE instead of working in the command mode.
After completing these tasks I want to delete KDE and working ahead in command mode.
How do I install it (may be I can install it from the CD's) and how do I uninstall it if I am ready?
You did not specify your distribution, so I can only give you the most generic answer: use your package manager to install and uninstall KDE (arts, kdelibs, kdebase, etc.)