When you capture a picture or use an external file for a picture, Dr.Explain pulls a copy of the picture into the Dr.Explain project.  The result is that you DO NOT NEED TO make or keep a separate copy of that image as a part of your Help source files!  The only source file is the Dr.Explain project itself, and it contains everything needed to generate the CHM, HTML, PDF and RTF outputs.  This is unlike HTML Help projects under Microsoft HTML Help Workshop where there are dozens or hundreds of source files, and if even 1 gets lost, it is a disaster.