[PaulR]

As others have pointed out, a watermark with copyright in it covers you from a legal perspective. Anyone who reuses your images is breaking copyright laws. Here's a free program to add watermarks.http://www.freedownloadscenter.com/Multimedia_and_Graphics/Misc__Graphics_Tools/uMark_Lite.htmlAs Sam Adams points out, anyone who is savvy can defeat all methods. Watermarking/copyrighting simply will make your images less appealing for people to steal, but will never prevent it. It will prevent the less savvy from simply downloading your image and calling you their girlfriend, at least they'll have to work at it.Good luck.