Truble

The vast majority of computer problems a help desk person faces can be solved by drilling down to find the actual problem.  If your very good, the person on the other end of the phone does not feel like a total idiot.  

"The trouble with computers, of course, is that they are very sophisticated idiots." - Doctor Who

There are very strict rules that a computer can follow and getting a computer to stop following a set of rules can be quite the task. 

In laymans terms...  Let us say that someone calls you on the phone to complain that the ducks are eating all the Buicks.  Now you know that ducks cannot ingest a Buick and that this is not remotley close to duck behavior.  Now you could just state the obvious fact and hopefully go back to inputting numbers into a spread sheet.

"Ducks cannot eat Buicks,  Good day to you SIR!"

This will not allow you to hopefully go back to inputting numbers into a spread sheet, rather this will start a useless discussion about the eating habits of ducks..

So the course of action is to find out as much about the callers duck gastronomic incident.

Exactly where was the duck eating the Buick?  Did the duck eat the entire Buick?  Did you see the duck actually chomping on the Buick? What did the duck look like?  What did the Buick look like?  Have you seen a duck eating a Buick before?  What medication(s) are you on?

The various drill down questions will lend out tiny bits of information that will allow you to build the actual question.

"So what we really need to know is why the  duck eating in front of Buick made the car disappear"