I totally agree with Toxaris, you better use a third-party application to edit (re-size, change quality, apply effects, crop and so on...) images before inserting them into MS Word. Perhaps,
GIMP may helps you.
But remember, you still can remove cropped areas of an image using MS Word. Click
Compress pictures command in
Picture tools - format tab and click
Options... button to do this. This article will help you to do that:
5 Tips for Optimizing Images in Word Documents