Unchecked already and still popping up?
I'm going to be honest man, based on this and the Babylon search thread, your computer is probably seriously messed up. At this point, the best option may be to save everything important, preferably to something like an external hard drive, and reformat the HD and reinstall the OS on the computer. It will put everything back to the default settings and hopefully remove the junk that's on there. Install Avast (free) or another good antivirus and find game websites for your son that are known to be safe. You will lose everything on the HD that isn't saved somewhere else.
Does your computer have a good restore point saved? If not, wiping it clean will probably be the easiest solution at this point. There's no telling what all is on there.
Also, it's probably not a good idea to do any online banking or anything involving your personal info on this computer.