Three men are in a hot-air balloon. Soon, they find themselves lost in a canyon somewhere. 
One of the three men says, "I have an idea. We can call for help in this canyon and the echo will carry our voices far enough for someone to hear us." 

So he leans over the basket and yells out, "Helllloooooo! Where are we?" (They hear the echo several times). 
15 minutes later, the men in the balloon hear an echoing voice: "Helllloooooo! You're lost!!" 
One of the men says, "That must be a Microsoft service tech!" 
Puzzled, one of the other men asks, "Why do you say that?" 
The man replies: "For three reasons: 
(1) he took a long time to answer, 
(2) he was absolutely correct, and 
(3) his answer was absolutely useless."