I came across the following when I was researching something. I would never need to use it because I am the only person using my PC, but for anyone who have kids who may use their PC, this seems like it would be really good.
http://www.microsoft.com/protect/products/...teadystate.mspx

It's nice that Microsoft gives it away for free it, and from reading about it I think it goes beyond their avocation of protecting a computer from children changing things since anyone can be stricken with an infection with all the malware that's floating about. Sounds like something which should be built into Windows by default!

There are however other alternatives like Sandboxie, or Returnil Personal Edition of course coupled with WOT for web browsers.

What I found good about this was the fact that supposedly a reboot clears anything that was manipulated on your PC. I guess that would be handy if kids were fooling around with stuff during their session, in which case its doubtful they would have used Sandboxie or Returnil.

Nice one. Thanks, razz. I am about to set up a computer for a child, it will be very useful.

For children under 12 and children doing stupid thing with their computers, this is useful (and, if I'm not mistaken, it was built into Win7 Beta but they removed it from the RC, it was called "guest mode").
For every other children, this is stupid. If you don't want your children going to porn sites or downloading bad software (keygens / reg cleaners / ...), just explain them why this is not good.
If you restrict their access to a lot of things, they'll have only one idea in mind : Crack your parental control to see what you don't want them to see. And they'll not like you.

Frank Barone - "....deny them water!"

I very much agree here. Explanation is better. I also every bit of software like this i have seen can be disabled via the registry, even if it locks 'run' .