Wordpress Theme Drop Down Menu Help needed - hide Child Cat

Hi

I need some help in my wordpress theme drop down menu which can be seen in this demo page:

http://www.wpzoom.com/zenko/demo/

It is using the same wordpress theme but my site has Child Categories and I want to stop it from appearing in the drop down menu as can be seen in the picture. Please assist.

Thank you

This is the Menu.js file that I found in the theme

sfHover = function() {
	if (!document.getElementsByTagName) return false;
	var sfEls = document.getElementById("nav").getElementsByTagName("li");
	for (var i=0; i<sfEls.length; i++) {
		sfEls[i].onmouseover=function() {
			this.className+=" sfhover";
		}
		sfEls[i].onmouseout=function() {
			this.className=this.className.replace(new RegExp(" sfhover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", sfHover);

Code (markup):