This guide might be a little different from the others because I write this for the Windows users. Here’s how to convert Microsoft OpenXML docx files to odf OpenDocument files (and vice versa) in Windows using only commandline :
Odfconverter also supports converting Open Document files (ODF, ODP, ODT) to OpenXML files (PPTX,DOCX,XLSX) making it a handy tool to use.
Why odfconverter?
Odfconverter is a (relatively) small and compact standalone tool for converting Office 2007 files to their OpenDocument counterpart. The convenient batch mode conversion makes it attractive tool to use when converting multiple files between the two formats.
The only downside with this converter is that it does not convert mathematical formula pretty well compared to other features.
[Source OOOninja]