This fellow is looking to buy a saw to cut down some trees in his back yard.  He goes to a chainsaw shop and asks about various chainsaws.  The dealer tells him, "Look, I have a lot of models, but why don't you save yourself a lot of time and aggravation and get the top-of-the-line model.  This chainsaw will cut a hundred cords of wood for you in one day."

So, the man takes the chainsaw home and begins working on the trees.  After cutting for several hours and only cutting two cords, he decides to quit.  He thinks there is something wrong with the chainsaw.  "How can I cut for hours and only cut two cords?" the man asks himself.  "I will begin first thing in the morning and cut all day," the man tells himself.  So, the next morning the man gets up at 4 am in the morning and cuts and cuts, and cuts till nightfall, and still he only manages to cut five cords.

The man is convinced this is a bad saw.  "The dealer told me it would cut one hundred cords of wood in a day, no problem.  I will take this saw back to the dealer," the man says to himself.

The very next day the man brings the saw back to the dealer and explains the problem.  The dealer, baffled by the man's claim, removes the chainsaw from the case.  The dealer says, "Hmm, it looks fine."

Then the dealer starts the chainsaw, to which the man responds, "What's that noise?