I realise this won't help in this case, but I have built or configured countless PCs and laptops for friends etc over the years, and since most of these were not computer-literate people many of them eventually got infected with various stuff.
In particular any PC used by a child is likely to have a useful life measured in months if not weeks
Obviously you cannot get infected if behind a NAT router (as most people are) but infections come to you by email or from infected websites. AV software (esp. Kaspersky) catches most of them but not all, and once infected most infections cannot be cleaned by any software (because they have damaged windoze files, etc).
So in most cases the infections are simply too complicated to remove. You might find it and apparently remove it, but it has done damage and the PC doesn't work properly.
On top of the infection itself, the user has often trashed the machine by doing something silly.
The only way to deal with this stuff is to install (in my case; there are other similar tools)
Trueimage before the delivery of the machine, make a boot CD and store that somewhere (I used to give it to the "customer" but they tend to lose them) and then do a full image backup of the HD. This often fits onto a DVD (dual layer perhaps; 9GB) but in some cases I just store the image on a 2TB network drive.
Then when the customer comes back asking for help to clean out a trashed machine (which IME is guaranteed to happen within 1-2 years) I just copy off what data one can copy off (e.g. jpegs, docs, etc) to a DVD, and restore the image. This is what computer shops used to do and it is all they can do.