ParentalControl Bar is a free website blocking application for Windows that lets you block all attempts of accessing websites which contain any type of adult content.
The program is protected with a password which only the adult who installed the program should know. Access to all adult content is automatically restricted.
This content is fully configurable within the setting options, where you can define the specific content which should be blocked (sex, nudity, violence, etc.).
All of this makes ParentalControl Bar a great tool that is definitely worth downloading.