Gallery full browser pop up not working for older IE

I have a pop-up gallery that doesnt work in older versions of IE…know a solution?? heres my code… It works perfectly in new IE7 and FireFox

chuw_btn.onRelease = function() {
getURL ("javascript:NewWindow=window.open('http://www.akmphoto.net/chuw.html','newWin','width='+screen.availWidth+',height='+screen.availHeight+',left=0,top=0,toolbar=No,location=No,scrollbars=No,status=No,resizable=No,fullscreen=No');  NewWindow.focus();     screen_height = window.screen.availHeight; screen_width = window.screen.availWidth; left_point = parseInt(screen_width/2)-(800/2); top_point = parseInt(screen_height/2)-(720/2); setTimeout('NewWindow.moveTo(left_point,top_point)',100); void(0);");
}