You can use LaTeX2HTML. Perl based It will convert the entire document, but one side-effect is that all the formulae are converted to images. L2P. Perl based. Uses imagemagick. Just the math - you pass in the equation on the command line. There is latexmath2png. Python based. Just does the math. Install LyX. Write your equeations and save as a Word doc.
The conversion tools could be run in windows, but they are mostly intended to run under linux. On windows they might require some tweaking. LyX runs just fine in mac, windows & linux."