The only thing downloaded was a free anime drawing program. Good lesson for the kid - NOTHING IS FREE!
Kids will download and install anything that looks cool. Firewalls and antivirus software are useless — firewalls because downloading is an outbound connection and antivirus because they just can't keep up. Never do anything sensitive on a computer shared with a kid. If you are really paranoid, put your own computer behind an inner firewall.
A few years ago, my sister asked me to fix a computer her kids had been using. I had to rename the Task Manager app in order to see what was running, because there was a service running that would kill it as soon as it was started. I backed it up, wiped the disk, reinstalled, and selectively restored from the backup.