Is there a freeware snoop program for watching kids' activities on Windows?

Something akin to Spector payware is what I'd like to locate, only free.

This spyware would only be installed on machines with administrator rights,
the firewall would have to know about it, and it should report keystrokes,
emails, chats, and web pages. It's ok if spyware scans find it as my kids
don't do the scanning (or so I hope).

Does decent freeware snoopware exist for watching over teenagers' activity?