If you like to open .docx files without Office Word 2007, there’s a new Firefox extension from Microsoft that should help. Available for Windows as well as Linux machines.
Open DOCX files as an HTML document in any web browser
There’s a command-line version of OpenXML viewer (download link) available as well for converting docx documents into HTML files that you may then open in any other web browser.
Other alternatives for reading docx files without Microsoft Office 2007 include Internet Explorer, Gmail, Email, Word viewer and the converter for Mac.