How to block porn completely
Use internet security program like Kaspersky,ESET (in Latest Version 5 released in 2011), Bit Defender etc. they have built in support for parental control (Password Protected). U can create a user which u want to set parental control and can block specific item and give access what type of site you want to give.
For more information check the installation documentation for the antivirus or internet security program whichever you have purchased. (ONLY for HOME USERS).