In cart v4.28 and earlier to remove the lightbox feature you need to comment the following lines of javascript in the productdetail.ascx page as follows:
<%--Lightbox Live Server--%>
<%--<link href="/css/lightbox.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="/js/prototype.js"></script>
<script type="text/javascript" src="/js/scriptaculous.js?load=effects,builder"></script>
<script type="text/javascript" src="/js/lightbox.js"></script>--%>
Also, there is an ie9 fix for lightbox available please see the following forum post http://www.smith-consulting.com/Forum...
Starting in cart v4.30 we replaced lightbox with fancybox. Fancybox provides the same effects as lightbox but doesnt have the ie9 issues. Also, starting in cart v4.30 the javascript for lightbox and zoom effects is dynamically enabled in code behind and doesnt require you to comment/uncomment the javascript in the productdetails.ascx page.