An article that will be published in the next Journal of Intellectual Capital (Andriessen, 2006) will show that there are at least 22 different metaphors that we use to think and talk about knowledge.
KB article. Problem can happen if you have the daemon tools installed and need to overinstall windows - check this article if your CD/DVD magically has disappeared...
S. Staab, J. Lehmann, and R. Verborgh. Companion Proceedings of the The Web Conference 2018, page 885--886. Republic and Canton of Geneva, Switzerland, International World Wide Web Conferences Steering Committee, (2018)