Need your suggestion of blocker or something like this

Hi, this really really has puzzled me for several days, so my sister has asked me to install some form of parental control on her two computers. It seems she caught her son looking at... things. I've offered to examine all these sites for suitability and got a shocking look!!! Seeing as how he's still fairly young and has very little computing expertise, parental control should be pretty effective for a good deal of years.
I was looking at McAfee Internet Security Suite, but it doesnt talk much about its parental control system. But google recommended some following: OpenDNS (a great many are talking about it, but it seems not a parental control, why?), SentryPC, Porn Blocker, K9, but I have no idea which one to use though (and the way). Pretty much all it needs to do is block questionable websites, and provide some kind of whitelist thing so it won't block cracked. Any of you has experience with such kind of? Or some other nice advice? Thank you!
Oh, We all are not savvy enough for computer so I just paste her My Computer- right click
OS: Win XP Pro SP3
Pentium (R) Durl-core CPU
E5300 @ 2.60GHz
2.59GHZ 2.00GB

there is a program called K9 web protection http://www1.k9webprotection.com/ which works awesome also you can use open DNS servers with a free account you can have a filtering control to block various sites also http://www.opendns.com/