Not to change the subject.. but that's another question I have! How do I even make a slideshow? I've never done it. What program is necessary? I would love to make something that plays to music and they can pop into their DVD player..
A simple way to take digital photos on a computer, is to "Print screen", and then open in photoshop and paste it. The best thing to do is don't give a high resolution image to the person. And to put a watermark on it.
This would be extremely easy to do in a program like iMovie. It would probably take fifteen minutes, and the final output would be in a movie format, which would make it easy to view, professional looking, and more difficult (though still fairly easy) to steal from. You could give your client a CD with an mpeg file.