The HPJ file is the main organizational file, containing all the source files. When generating WinHelp, RoboHelp creates an HLP file and a CNT file. The HLP file doesn’t contain topics excluded by a conditional build expression, so the new project might not mirror the original.
You can import HLP files to HTML-based projects, but the process is easier if you have the HPJ file.
You can’t output a WinHelp file from RoboHelp HTML.