We had posted about free online watermarking tool and another desktop based tool called Pixillion which allows you to convert, resize and watermark images in bulk. Add WalterMark is another free to use useful utility which lets you add watermark in multiple images, photos or pictures.
With this program, you simply point to the folder containing the originals, pick a font, preview the first image and click "Apply". The program will create a new "WalterMark" folder within the selected location and copy each photo and add the watermark.
This application is very simple to use, you can add watermark images in bulk in a specific folder, it will also take images in sub folders inside a folder path you defined. This program seem to work on all versions of windows we have just tested it on windows 7 ultimate 32 bit.