Rage against the machine
The 'Bad Day' clip may have been a set-up, and 'Howard the Happy Paper Clip' - linked to from the right-hand column on this page, under Just for Fun - was definitely play acting, but this week Usability News reports on a real case of computer rage, originally reported in Personal Computer World. Armed police swoop on PC rage row recounts how a SWAT team was called in to deal with a gun-toting man who wanted to kill his computer, which he described as "the bitch". This all happened in Boulder, Colorado.

This University of Maryland site has some material about effective but non-dangerous methods for engaging in computer rage - you might also want to complete the accompanying survey. A BBC article on the subject a while back generated these real life descriptions of anger at computers.