How to use Group Policy to block user internet downloading?

I have a computer for my kid, the OS is XP professional, I create only one administrator account for him(for my personal reason, I want my kid use administrator account only, not limited account, not other accounts). I allow my kid to access internet, but I don't want my kid downloading any software from internet and installing the software to his system. Can I do that by using the Group Policy and how to do it? I also want to completely prevent my kid installing any software on his own from cd-rom, usb or internet, how can I do that by setting up the group policy?

I have created the Group policy Editor console, I go through the computer configuration and user configuration, But I don't see anything that I can use to prevent internet downloading and software installing. Anyone have some suggestions, thanks a lot!