When you change your code to be:
Code:
<?php echo 'ORDER TOTAL: ' . $order->info['total'] .  ($order->info['total'] < 100 ? 'YES' : ' NO') . '<br>';?>
 <?php if ($order->info['total'] < 100.00) { ?>

                                    <div  class="alertInstalmentsShadowedOut"><?php echo  zen_image(DIR_WS_TEMPLATE . 'images/instalments_shadowed_out.gif');  ?></div>

                                        <?php } ?>
[/CODE]

You should see on the screen an echo of:
ORDER TOTAL: YES (when order total is < 100)
-- or --
ORDER TOTAL: NO (when order total is >= 100)

What do you see using the code above?