You coould always just use XSLT. Suppose your original XML is more along the lines of:

<NikuDataBus>
  <Header name="xyz">
    <Customers>
      <customer name="x">
        <address>1313 Mocking Bird Lane</address>
      </customer>
      <customer name="y" />
      <customer name="z" />
    </Customers>
  </Header>
</NikuDataBus>
[download]

then an XSLT stylesheet such as this would do the trick:

<xsl:stylesheet version="1.1"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:output method="xml" version="1.0" 
  encoding="UTF-8" indent="yes" />

<xsl:template match="customer">
  <xsl:variable name="outFile" 
    select="concat('customer.', @name, '.xml' )" />
  <xsl:document method="xml" indent="yes" href="{$outFile}">
<NikuDataBus>
  <Header name="xyz">
    <Customers>
    <xsl:copy>
      <xsl:copy-of select="*|@*"/>
    </xsl:copy>
    </Customers>
  </Header>
</NikuDataBus>
  </xsl:document>
</xsl:template>

<xsl:template match="NikuDataBus">
  <xsl:apply-templates select="Header/Customers/customer" />
</xsl:template>

</xsl:stylesheet>
[download]