Unfortunately, we don't have much first hand experience with a good Windows solution. However, we did a little research and this looks like it could be a good app that will do the trick: https://imageresizer.codeplex.com/
If you like the look of it, you can download the application here: https://imageresizer.codeplex.com/downloads/get/347439
We have also included instructions on how to resize images using Paint: http://windows.microsoft.com/en-ca/windows7/resize-a-picture-using-paint
If you personally have any good Windows software you could recommend to others, let us know and we'd be happy to pass on the info!