http://www.faststone.org/download.htm
After you download click the file you have downloaded to install it.
Steps to resize:
1. If you haven't already done so open up the program you have just installed. On the right side you will see a window labeled "source" for browsing folders, browse to the folder which contains your images and click the "add all" button. This will place all the images in that folder and subfolders in the left pane. The left pane is a list of images that you want to convert. If you only want to convert a few images click each one individually in the right pane then click the "add" button to add them to the right pane one at a time.
2. To specify a output folder for your newly resized images, below the left pane and to the right of "output folder" click the "select" button on the right. This will open up a "select folder" dialog box. By default your desktop is selected, click the create button on the bottom of this dialog box to create a new folder on your desktop where your new resized images will be saved to. Note: the original images will remain untouched, this is important since resizing results in loss of detail for printing purposes. The sizes we're going to use in in the following steps are more than adequate for viewing on a monitor.
3. Put a check mark next to "Use advanced options" then click the "options" button to the right which will open up the advanced options dialog box.
4. By default you should now be on the resize tab, put a check in the box next "use resize" which will make the resize options available. On the top select "in pixels", in the height and width entry box type enter 1200 in both, put a check next to "preserve aspect ratio". Then click OK on the very bottom. These settings will resize your images to a max of 1200 pixels either height or width, whichever is greater. By checking the "preserve aspect ratio" box it will keep the image in the correct perspective.
5. Click the start button. That's it, your done
All the images in the output folder will have a max width or height of 1200 pixels. You can now upload them to the file gallery.
