This site and
this site also appear to offer fairly informative removal information. I was a bit surprised not to see a number of Google hits referring to forums that "do" HijackThis logs, so I guess it might be fairly new.
Superantispyware is a good, reputable, thorough scanner. Free version available.
There were a lot of Google hits referring to keygens and cracks. Appears this rogue antispyware is usually installed when attempting to install fake codecs. The message for your son should be clear.