The image is stored in Word as EMF format -
http://www.gmayor.com/extract_images_from_word.htm will extract the images as EMF and the simplest way to convert the resulting files to PNG etc is to use the batch function of SnagIt. SnagIt is not free, but there is a working trial, and frankly it's one of the most useful tools in my toolbox that I could not manage without and I use it every day.
It is worth saying that you could have used SnagIt to capture the text directly to png etc in the first place.