PC Laptop-based porn blocker

Hey. What is the best porn blocker that people here use? I was using Covenant Eyes but it did something weird to my computer and I tired Net Nanny after that which was a disaster...I do not trust myself with my computer in the house under ANY circumstances at all so I keep it in my car and only use it at the public library which is tremendously helpful. But I need my computer for school & work online so it's a huge inconvenience to have this situation. What good, helpful porn blocking programs people use? Not browser-based but for the whole laptop.