Close, but for the products in the side bar you change the intermediate.php file to:
<li><span><a href="<?php echo($assumedRoot); ?>Products_Detail.php?ProductID=<?php echo $row_ProductMenu['ProductID']; ?>&CategoryID=<?php print $row_ProductCategories['CategoryID']; ?>"><?php print $row_ProductMenu['ProductName']; ?></a></span></li>