Your question was already answered on Meta Stack Overflow.
- How does deleting work? What can cause a post to be deleted, and what does that actually mean? What are the criteria for deletion?
- How can I delete my post on Stack Overflow?
Also from their Why and how are some questions deleted? page:
Users can delete their own questions if the question:
- has zero answers
- only one answer, but that answer has no upvotes
Simply click the delete link underneath the question.
You can vote any quesiton or answer if you see this: