Starting with HelpNDoc 8, *.doc documents can't be imported anymore. You can use an external application such as Microsoft Word to convert the legacy *.doc file format to the recommended *.docx format.

Starting with HelpNDoc 7, *.docx documents are imported by HelpNDoc without the need for any third-party software.

For earlier versions, the free "Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint File Formats" must be installed on some systems in order to import Microsoft Word *.doc or *.docx files. It is automatically installed with some older versions of Microsoft Office but not with the latest versions. It can be downloaded from https://www.helpndoc.com/downloads/office-converter/FileFormatConverters.exe