If I "Generate Sample Xml", it always generates an unrequested qualifier (ns0). I will use the example provided by SUN 
in the article "Namespaces in XML Schemas, Part 1: An Introduction, Chris Webster and Marina Sum, Updated: October 30, 
2006".
Here is the "po.XSD":

<?xml version="1.0" encoding="UTF-8"?>

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
	 xmlns="http://www.w3.org/2001/XMLSchema/po.xsd"
	 targetNamespace="http://www.w3.org/2001/XMLSchema/po.xsd">
             
<xsd:element name="purchaseOrder" type="PurchaseOrderType"/>

 <xsd:element name="comment" type="xsd:string"/>

 <xsd:complexType name="PurchaseOrderType">
   <xsd:sequence>
     <xsd:element name="shipTo" type="xsd:string"/>
     <xsd:element name="billTo" type="xsd:string"/>
     <xsd:element ref="comment" minOccurs="0"/>
   </xsd:sequence>
   <xsd:attribute name="orderDate" type="xsd:date"/>
  </xsd:complexType>
 </xsd:schema>

This is the generated SAMPLE XML (po.xml). Please note the  "nso":

<?xml version="1.0" encoding="UTF-8"?>

<!--
    Document   : po.xml
    Created on : 22 de septiembre de 2008, 04:23
    Author     : Hans
    Description:
        Purpose of the document follows.
-->

<ns0:purchaseOrder  xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance'
   xmlns:ns0='http://www.w3.org/2001/XMLSchema/po.xsd'
   xsi:schemaLocation='http://www.w3.org/2001/XMLSchema/po.xsd po.xsd'>
        <ns0:shipTo></ns0:shipTo>
        <ns0:billTo></ns0:billTo>

</ns0:purchaseOrder>

Thank you.