Greenshot is a free image annotation tool that allows users to capture screen shots or select an image file for annotation.
Make sure to click on the Downloads link because there are other advertisement downloads on the screen. See below:
Using Greenshot for annotation:
Right click the Greenshot icon located on your start bar or the hidden icons box
Select the “Open image from file” option. Note: do not resize the image for annotation otherwise it will not work correctly with the original image.
Select the image you want to annotate from the file and select the Open in image editor option.
Greenshot has all of the standard annotation tools. Annotate the image as desired and then “Save as”. Do not just save the image or you will lose the original, un-annotated image.
Greenshot has excellent help files and will take you step by step through any process from capturing a screenshot to all the settings. Greenshot help is located at http://getgreenshot.org/help