When Microsoft shifted from Office Word 2003 to Office Word 2007, the formats for Word documents changed from .doc to .docx as well. But now MS has made .docx as a permanent standard for Word documents and it will be long before they change it in future. Word 2010 saves the word documents in .docx format too which means that every tool that can open .docx formats of Word 2007 would have no difficulty in opening .docx formats of Word 2010.
In layman’s terms, there is no difference between the docx format of Office Word 2007 and the docx format of Office Word 2010, both are same.
Docx format can be opened by various online and desktop tools. The two most common web apps to open docx formats are Google Docs and Zoho Viewer. They even allow you to edit the documents and share/embed them quickly.
For desktop tools I would recommend going for OpenOffice which allows you to edit the document as well. But if you just need a simple tool to view the docx file, then you can grab Word Viewer which is developed by Microsoft. But remember that Word Viewer requires Microsoft Office Compatibility Pack, so install it as well.
Update: Also check out TextMaker Viewer 2010. An awesome free desktop application to view docx documents.
Updatee 2: We have reviewed yet another word processor which promises to be faster, lightweight, and offers more features. Check out DevVicky Word 2010.
What is your favorite way of opening docx formats? I would vote for Google Docs, but other alternatives can also come handy.