isnt there a program that can make a map and find the wireless users house? a friend of mine has a program that does it but i dont know the name of it, but he uses it to find people who are tapping into his wireless. but that would be the safest way, find his house and knock on the door:P

otherwise id just go in and leave a text file on his desktop named READ ME NOW.txt saying "fix your xxx xxx before some bad kid with too much time hurts your box" anonymously