So this is what I wrote:
<a href="xxx.jpg" onclick="window.open('xxx.jpg', 'window_name', 'width=400,height=400,resizable=yes,scrollbars=yes'); return false"><IMG border="0" alt="Click here to view a close up of this condition." src="xxx.jpg"></a>
However the new window "intelligently" resizes xxx.jpg to fit in it, which completely misses the point. How can I make it leave the picture in its original size?? Please help! I'm using XP.