Problem: When saving an invoice (or another document) as a file, the dropdown list in Save As dialogue only shows .rtf and .pdf options.

Neither .doc mor .docx are displayed.

Solution: 

Translation Office 3000 and Projetex use some parts of the MS Word application and the entire MS Office suite to export documents to DOC and DOCX, so it is required to have MS Office installed in order to save documents in the Word formats.

Please install MS Office and try again.

If MS Office is already installed, please make sure it is registered properly in your system.
Please open the registry editor (type 'regedit' in the start menu search field), then navigate to 

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\WinWord.exe

If there is no such folder, please re-install MS Office.