Why does my LARGE image window not scroll?

I have 800x800 large image for the main BIG picture.
The image is too big to fit on the screen so the bottom 1/4 or so does not show. Other sites there is a scroll bar on the right side of window so you can scroll down to see the bottom of the image. Not on MY large image though! No way to see that bottom 1/4 of the product.

Here is an example what I mean.
This url for just the large image will give me the scroll bar so I can view the bottom of image.
http://shirts-and-stuff.com/zenstore/index.php?main_page=popup_image&pID=431
But only when I use it in a new window, like clicking this link.

I copied that url from the window Zencart opens to show the image on my site, but in the Zencart opened window there is no scroll bar so the bottom button of vest and everything lower is cut off, and cannot scroll down to see it.

Here is a link to the item page, click to get the large image from here to see what I mean.
http://shirts-and-stuff.com/zenstore/index.php?main_page=product_info&cPath=1_24&products_id=431

Is there a setting I need to change somewhere? I do not understand why I have a scroll bar in a new window I open it in, but not in the window Zencart opens.

Thanks!

Hi

Were you able to fix it? I just tried both links and both windows give me a scroll bar

This appears to be related to the java script or at least call to it. Found this line using firebug for firefox when looking at the javascript:

function popupWindow(url) {     window.open(url,'popupWindow','toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=no,resizable=yes,copyhistory=no,width=100,height=100,screenX=150,screenY=150,top=150,left=150') 
} 

In this line states to have scrollbars=no... If that were yes, then they would be available...