
Computer Error or User Error?
In general, you should assume that an error is caused by the user.
Sure, once in a while you may find situations where a problem is caused by a system bug, but human beings are certainly more faulty than computers. In general, the best way to figure out what has happened is to ask the user what he was doing - if he answers with the classical "nothing, nothing wrong", he is likely the cause of the error.
Besides, most systems contain utilities, usually called "Event Viewers", which allow you to easily see a lot of information concerning a particular problem, and they''re very useful in any cases.