Take this part of your code:
while (!$directory->EOF) {
?>
<table width="100%" border="0" cellpadding="0" cellspacing="0">
<!--DWLayoutTable-->
<tr>
And replace it with something like:
$a = 0;
while (!$directory->EOF) {
$bgcolor = ($a++ & 1) ? '#ffffff' : '#eeeeee';
?>
<table width="100%" border="0" cellpadding="0" cellspacing="0">
<!--DWLayoutTable-->
<tr bgcolor="<?php echo $bgcolor ?>">
For further details, see:
http://www.faqts.com/knowledge_base/view.phtml/aid/783/fid/9