Flickr also shows image in different fixed sizes. He can right-click on the image and select 'save image as' in browser.
Gimp is not that hard. Install Gimp. Open Windows Explorer. Right-click on image file, choose Copy. (
test.jpg) Paste image in Windows Explorer. (Copy of test.jpg) Right-click on 'Copy of test.jpg39; and choose 'Open with->gimp win remote. (image is opened in gimp) on image menu: click 'Image->Scale image' a box pops up. Adjust height/width by pixel/percent/etc and click Scale. File->Save.