http://www.itwire.com.au/content/view/12608/1023/
"For reasons known only to itself, Microsoft has changed the default
equations editor of Word 2007 so that, unlike previous versions of Word, it
is no longer compatible with the globally accepted standard for writing
equations in documents, Mathematical Markup Language (MathML).
It is hard to believe that even Microsoft would be so arrogant as to expect
scientists and scientific publishers around the world to switch from the
globally accepted MathML standard just so they can use Word 2007. It almost
seems as if Microsoft is trying to drive the scientific community into the
arms of OpenOffice.org.
In any case, as has just been demonstrated by at least two important
publishers, the power to dictate standards in the documents space may be
starting to shift away from the world's largest software vendor and toward
the user community."
As usual, it is generally good practice to avoid Microsoft products whenever
possible.