If I understand well the question is : How to remove recently added products from cart sidebar ?
If I am right, open yourtheme/template/checkout/cart/sidebar.phtml.
If this file doesn't exist then copy base/default/template/checkout/cart/sidebar.phtml and past it to yourtheme/template/checkout/cart/sidebar.phtml.
Remove the following code :
<p class="block-subtitle"><?php echo $this->__('Recently added item(s)') ?></p>
<ol id="cart-sidebar" class="mini-products-list">
<?php foreach($_items as $_item): ?>
<?php echo $this->getItemHtml($_item) ?>
<?php endforeach; ?>
</ol>
<script type="text/javascript">decorateList('cart-sidebar', 'none-recursive')</script>
In case you didn't copy sidebar.phtml from base/default theme and past in yourtheme/template/checkout/cart/ then maybe it will not be exactly the same piece of code but for sure you'll find
<ol id="cart-sidebar" class="mini-products-list">
Remove it and the title just before