Once upon a time the Word .doc format was the de facto standard for word processing. Then Microsoft went and mucked it up with Word 2007, which introduced the XML based .docx format.
To be fair it is an improvement on clanky old .doc but it also meant that older versions of Word were unable to open document written in Word 2007 or later. Again, to be fair, there is the free Compatibility Pack available from Microsoft, but what if you haven’t got Word, and you get sent a .docx file? Well, there’s always OpenOffice or you could download the free Word Viewer, but this is an old program and it has a number of limitations.
There’s another alternative, how about TextMaker Viewer 2010. It will not only open password protected .docx files it also handles OpenOffice documents and a number of other popular word processor document formats.
Needless to say you can’t edit documents but they can be printed and exported as pdfs. There’s no catch, it’s free, though there is an annoying ‘nag screen’ but this can be disabled after the third time the program is opened by ticking the ‘Do not show again…’ box.