A helicopter pilot is flying to Seattle and hits a pea-soup-thick fog bank. He's completely disoriented, flies blindly around until he the spies the top few floors of an office building. He pulls up real close to it, gets the attention of a woman sitting at her desk. "Excuse me!" he yells, "where am I?"
You're in a helicopter," the woman replies.
The pilot pulls off sharply to the left, takes one or two crisp turns through the dense fog and then does a perfect landing at the Seattle Airport.
"That was amazing!" says a passenger. "How did you know from her answer where you were?"
"Easy," says the pilot, "her answer, while correct, was absolutely useless. So I knew I was at Microsoft tech support."