I had a similar situation with my ex. She wanted the PC to be restricted for
her kids access. I installed "Net Nanny", which allowed me to block any
"unsuitable" content from being accessed by her kids.
There were 2 of them, so I set up seperate accounts with different settings
(One was more prone to look for porn than the other one)
.
It also allowed me to lock the computer on either a time-basis (like, once
they should be in bed) and ban sites that contain sexually explicit images.
I would recommend Net Nanny to anyone who requires this kind of internet
restriction. It takes a while to sit down and learn how to configure it
properly, but it would be worth it if you're worried about what your kids
access.
Oh, and not only did it monitor internet, but it could block chat rooms,
yahoo + msn
messenger, and send me an email once a week with a full report which I could
see what child tried to do what!