AutoResizer is a FREE tool which automatically :

Finds all image files in the source folder
Resizes the images to your new dimensions
Change formats (JPG, PNG, or TIFF)
Add a prefix and/or postfix
Puts the resulting images into your destination folder
(your originals images are untouched)

Use AutoResizer to resize and reformat dozens, hundreds, even thousands of images quickly, efficiently, and easily.