[cflsystems]

In skin1/customer/main/product_details.tpl find this code

    <tr>
      <td class="property-name">{$lng.lbl_sku}</td>
      <td class="property-value" id="product_code" colspan="2">{$product.productcode|escape}</td>
    </tr>

and comment it out like this

{*     <tr>
      <td class="property-name">{$lng.lbl_sku}</td>
      <td class="property-value" id="product_code" colspan="2">{$product.productcode|escape}</td>
    </tr>
 *}