Website limitation / report system

[zenmasterbob123 () gmail com]

List;

I have teenage boys.  They are good kids, and generally don't get into a lot of trouble online, but the problem with 
raising a genius or two is that they are constantly curious, and I can't be over their shoulders 24x7.

I want to keep them away from the black hats and pervs in the interwebs.  I don't mind if they know I'm doing it.  I'd 
like to be able to block some sites outright.  One is running XP Home, and the other is running XP Pro.  I have a 
Windows 2003 Server and a WLAN.  

I could do ICS through the server, or I could a host-based package on each system.  I've also considered going to Vista 
for the new Parental Controls it has on board, but I figure if it's part of a MS OS then they must have gotten the 
tech, or at least the idea, from somewhere else.  I'd prefer freeware, of course, but I'd like to know what the list 
thinks.