Computer Help!?

We have a Windows XP comp and many suer accounts. I ahve an admin account and my son has a limited account. Lately he has been watching a lot of gory films I don't want him to see. Is there a way I can block the website he goes to? I tried the content advisor on IE but everytime I went to a website it would tell me to type a poword and put it on a aprroved list. Is there a way I can restrict the website my son goes to without having to go through that tedious process?