I would let him know about the damage his kid caused the last time. I'd also set an ultimatum if it happens again that you don't feel comfortable loaning out your laptop if its going to come back "damaged" every time.
Oh yeah, backup anything and everything you can. Just in case.
"i would never use a firewall, even without a router protecting me. Firewalls are just wastes of memory."
name omitted to protect the innocent
the cake is a lie