<?xml version="1.0" encoding="UTF-8"?>
<config>
  <modules>
    <Namespace_Module>
      <version>0.0.1</version>
    </Namespace_Module>
  </modules>
    <global>
      <resources>
          <module_setup>
            <setup>
              <module>Namespace_Module</module>
              <class>Mage_Eav_Model_Entity_Setup</class>
            </setup>
            <connection>
              <use>default_setup</use>
            </connection>
          </module_setup>
      </resources>
    </global>
</config>

<?php
$installer = $this;
$installer->startSetup();
$customerEntityTypeId = $installer->getEntityTypeId('customer');
$atttributeCode = 'display_name';

$installer->removeAttribute($customerEntityTypeId, $atttributeCode );
$installer->addAttribute('customer', $atttributeCode, array(
    'type' => 'varchar',
    'input' => 'text',
    'label' => 'Display Name',
    'global' => true,
    'visible' => true,
    'required' => false,
    'user_defined' => true,
    'visible_on_front' => true
));

$usedInCustomerAddressForms = array(
    'adminhtml_customer',
    'customer_account_edit'
);
$attribute = Mage::getSingleton('eav/config')->getAttribute('customer', $attributeCode);
$attribute->setData('used_in_forms', $usedInCustomerAddressForms);
$attribute->save();
$this->endSetup();