Wow, people sent him money and he never claimed it? Maybe that Powerbook is sitting on his desk and he's not motivated enough to put it in a box and mail it.

Seriously though, I've known people where: The more you tell them to do something, the less they do it. Some even get downright belligerent, shouting back empty reasons why they shouldn't do what is so clearly their responsibility. I've never figured out how to deal with this situation.