OpenXML Writer is an opensource editor that is able to generate the newly ratified Office OpenXML Wordprocessing files (extension .docx). The .docx files can be opened and further edited by Word 2007 and other softwares that support the Office OpenXML format. The Writer requires the .Net 3 Framework runtime to be installed on the user's machine. It supports basic paragraph formatting like justification and indentation. It also allows formatting of font sizes, colors, families and styles. On top of that , it includes a spell checker that can be toggled on or off.
OpenXML Writer is a freeware: there is nothing to pay in order to get and use it. The OpenXML Writer 1.2 free full version contains an installer and an uninstaller, and has a size of 67 Kilobytes.
For additional information and support request, please contact directly OpenXML Writer publisher.

OpenXML Writer Screenshot