Try going to this site.
on the right side third from the bottom is Image Resizer
Double click on the Imageresizer.exe and this will run on your computer.
Next navigate to the picture you want to resize, right click on it and you will notice in the dialog
box Resize Size picture as an option. Click on that and chose the size you want (large is good but smaller is better). Click OK and the
image will be saved with a change in the file name of either “Small, Medium or large” whichever
you have chosen. The original image will not be changed in any way.