I believe you will find something on these forums.

In a nutshell,, all you need to do is add the ligthboxt libraries to the page, and then, change the link of the enlarged image from a popup, to jsut a normal link with he lightbox class.

I'd say this lightbox is the easiest to use http://leandrovieira.com/projects/jquery/lightbox/

Hi Stacey

Did you get this sorted?  We have this on some of our sites if you are still looking to implement this.

We also have it on most of ours.  We use jQuery and a simple modal box to display not only the expanded image, but also special shipping conditions and other announcements from time to time.