When you build source code that was being made by VS6 in VS 2013, you may occurred this error message.
Building an MFC project for a non-Unicode character set is deprecated. You must change the project property to Unicode or download an additional library. See http://go.microsoft.com/fwlink/p/?LinkId=286820 for more information.
You can download Multibyte MFC Library for VS 2013. This add-on for VS 2013 contains the multibyte character set (MBCS) version of the Microsoft Foundation Class (MFC) Library.
http://www.microsoft.com/en-US/download/details.aspx?id=40770
Practical Security 