With Web Creator and Presenter this action can be performed with the Action tab of Image properties. Insert the image twice. Reduce the first one to an icon. Uncheck the Visible option for the second one. Make it appear when clicking or passing over the icon.

For older versions:

• Prepare two sizes of the same image, one small image and the other one of a larger size. Create a connection or link on the small image towards the large-sized file. When the user clicks on the small image, a new window opens with the large size. To return to the originating page, close this window.
  
• Insert the small image and make a connection or link towards a new page. On this new page, insert the large image with a connection or link back (or create a return button) to the previous page.
  
• Insert a button/choose "matrix image", the first file to be inserted will be the small one and the second will be the large one. You have the choice to click or to scroll over with the mouse. If you choose to scroll over, then insert the file of the large image second.