Here's the code that you can use in your source. Just specify dimentions of your window and source of your image.
<a href="images/image_name.gif" onClick="window.open('images/image_name.gif, 'YourName',
'status, width=800, height=600'); return false"><img src="images/image_name.gif" width="200" height="93" border="0"></a>
in this code you can use any image instead of image_name.gif. you can also modify window dimentions inside OnClick method 'status, width=whatever, height = whatever'
Hope this helps