How to Add Captions to Pictures in Your PowerPoint 2007 Photo Album
You can place captions under the pictures in your PowerPoint photo album. PowerPoint initially places the picture filename in the caption, but you can delete this caption and enter one of your own. To add captions to your photo album follow these steps:
Open the Photo Album dialog box.
On the Insert Tab click the Photo Album button.
Open the Picture layout drop-down list to Fit to Slide.
Layout options are displayed.
Click the Captions Below ALL Pictures check box.
It’s that easy! Now, all of your photos will have a line for captions.