you can add a javascript into the <head> of your site that will allow you to choose the size of the window as well as its values. a few things might have to be changed to suit your site. just add the function to your link.
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<SCRIPT TYPE="text/javascript"><!--
function popup(mylink, windowname)
{
if (! window.focus)return true;
var href;
if (typeof(mylink) == 'string')
href=mylink;
else
href=mylink.href;
window.open(href, windowname, 'width=450,height=450,scrollbars=no');
return false;
}
//-->
</SCRIPT>