What to do if attorney discovers child pornography in a computer that belongs to a member of a corporate client

Prof. Monroe Freedman has posted this interesting question at the Legal Ethics Forum:  A lawyer who represents both civil and criminal clients is at the offices of a corporate client he is representing in a civil matter.  While he is there, the lawyer gets permission from a VP of the company to use the VP’s computer  (which belongs to the corporate client) to check the lawyer’s email.  In using the computer, the lawyer inadvertently discovers that it contains pornographic pictures of sexual abuse of children.  The VP is not the lawyer’s client, and the VP has no reason to believe that he is.  The pornography is unrelated to the client’s business.  What should the lawyer do?  Go here for the discussion.