Magento – Madison Island Magento 1.9

Try setting the Use Web Server Rewrites value in Magento to No.

As mentioned in one of the other answers, the zoom feature starts in the createZoom function of the ProductMediaManager in /skin/frontend/rwd/default/js/app.js file.

So, another option is to override the individual createZoom function via JS later in the process.

For example, if you are inserting JS as a part of your own theme, then you can add the following to override the createZoom function in the ProductMediaManager object.

// ProductMediaManager is outside document.read scope
if (typeof ProductMediaManager !== 'undefined') {

  // Override image zoom in /skin/frontend/rwd/default/js/app.js
  // and prevent the zooming of images on hover
  ProductMediaManager.createZoom = function(image) { return; }

}

With this method, you don't have to copy the entire app.js file. However, you must make sure that your theme's JS is added after the parent theme's JS file. I find this to be a cleaner approach.