You could just set up your PC to send him a ping flood at random intervals; something like
ping x.x.x.x -n 50 -w 1 -l 65530
Replace x.x.x.x with his IP address.
It helps to have multiple windows open doing this to really flood the network. I'm not sure offhand how you'd program this though. Probably a visual basic program could do it quick. I know DOS programming though, not Windows. Just a thought anyway.
That'll send 50 x 65530byte data packets at his PC, which'll kill his own ping times....of course, thinking about that, there'd probably just be even more yelling then.
Or else go out to the circuit breaker box and flip the switch for his room/PC. Or a small radio-controlled switch in addition to his own power switch. Press a button in another room, and his PC will just begin to shut down.