"Open DNS" (which actually BLOCKS normal DNS service !) is malware that pretends to be a parental control facility but, whilst it does block some pornographic websites, it also blocks sites that do not pay it a fee to 'not block' it (protection racket). It is usually installed by the administrator on a network or by an ISP so there is nothing on your computer to find or remove. When I last experienced this it blocked yahoo but not google, it blocked dailymotion but not youtube !!
(the mighty) Tor bundle can easily bypass this. As we approach "Web 3" where everyone will only be allowed by their ISP to visit the websites that that ISP 'markets' I think that it is essential that everyone uses the Tor network most of the time (Tor does block flash videos as they can contain malware).