google for 'easy urpmi'. Install 'updates', 'main', and 'contrib'. This will allow you to get all the files you'll ever need. As to where to put them, when you install using RPM or URPMI, they go where the package installer tells them. ex: /usr/bin Keep your personal files under your home directory /home/yourname. That's how I keep from getting myself into trouble
I'll bet if you use MCC, mandriva control center,
to check and install updates, you're KDE problem will most likely go away...