I've recently created my second USB running backtrack 4 and at the startup of one session, I was asked if I wanted to install/configure (I am not sure what exactly they asked me: one or the other) KDE. Thinking it a part of my program installations, I completed the steps in its installation/configuration. Due to lack of time, I had to log off backtrack right after. When I launched backtrack that same day again, my whole interface had changed to KDE. WHat exactly happened? If it did change me from BT4 to KDE, which is better? Pros and cons?

Thank you for all who respond