The first thing I tend to do is to try and help the user make their question clearer and easier to read, to discourage the downvotes. If the question has value then it should be retained.
As regard to answering the question, sometimes the answer is "Get a professional in to help" If you can see from the question that the user is looking at getting themselves or their company into a lot of trouble (such as I delete my Exchange database, help!) then the best course of action is to make them see how much of a problem this is, and the best way for them to get out of this situation.
That said, if the question is not a critical problem, and the user would gain from learning how to solve this problem, then why not help them with their education. We all had to start somewhere, often this starting point was with the water way above our heads.