As Bitstorm said tho, really, it's an issue of child-parent communication about sexuality and appropriate use.
If he's like any of us, he'll find a way around it fast, like using a live disk, or a live usb, or and anonymous surfer with a securesite link, or he'll hack the hive for the pw.
If you want to know what was downloaded, set up an old box with linux and create a cache server, so he'll go through the cache server and there will be a footprint of everything.
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Ours is the age that is proud of machines that think and suspicious of men who try to.
H.M. Jones
They say "Sing while you slave, but I just get bored" - B.Dylan