What the hell is Untangle Web Filtering?

It blocks some of the sites I want to go on, and it bugs me, because my step-Dad doesn't use that to block the sites he doesn't want me to go on. It won't let me go on Myspace Videos-which I went on yesterday-, and other random sites I click on. Not alot..but still. How do I get rid of this? I'm cleaning my disc space right now. Also, how do I defrag my computer?