MOCPWEP2007FF enables you to open/edit/save Office 2007 documents in Office 2000, 2003, or XP without any work on your part. Just make sure that your office has the latest Service Pack installed – either SP3 for Office 2000 and XP, or SP1 for Office 2003.
If you don’t want to go all that difficulty and you just need to convert just a single .docx file, point your browser to docx-converter.com. Upload your file, select your preferred format (.doc is just one choice), and enter your email address. In a moment, you should get a note containing a link to download the converted file. It’s a free service.