Magento: Disable state/province option in checkout onepage

Sometime you want to remove the state/province option in the checkout onepage. Please do as following steps  Magento versions (up to Magento CE 1.7)
You have to edit 4 files:
- /checkout/onepage/shipping.phtml
- /checkout/onepage/billing.phtml
- app/core/Mage/Customer/Model/Adress/Abstract.php
-/skin/frontend/default/default (or your skin)/js/opcheckout.js
billing.phtml:
Comment out this Part:

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<div><code> <div class="input-box">  <label for="billing:region"><?php echo $this->__('State/Province') ?> <span class="required">*</span></label><br/>  <select id="billing:region_id" name="billing[region_id]" title="<?php echo $this->__('State/Province') ?>" class="validate-select" style="display:none">  <option value=""><?php echo $this->__('Please select region, state or province') ?></option>  </select>  <script type="text/javascript">  $('billing:region_id').setAttribute('defaultValue',  "<?php echo $this->getAddress()->getRegionId() ?>");  </script>  <input type="text" id="billing:region" name="billing[region]" value="<?php echo $this->htmlEscape($this->getAddress()->getRegion()) ?>"  title="<?php echo $this->__('State/Province') ?>" class="input-text" style="display:none" />  </div> </code></div> <div>

shipping.phtml
The same:

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<div><code> <div class="input-box">  <label for="shipping:region_id"><?php echo $this->__('State/Province') ?> <span class="required">*</span></label><br />  <select id="shipping:region_id" name="shipping[region_id]" title="<?php echo $this->__('State/Province') ?>" class="validate-select" style="display:none">  <option value=""><?php echo $this->__('Please select region, state or province') ?></option>  </select>  <script type="text/javascript">  $('shipping:region_id').setAttribute('defaultValue',  "<?php echo $this->getAddress()->getRegionId() ?>");  </script>  <input type="text" id="shipping:region" name="shipping[region]" value="<?php echo $this->htmlEscape($this->getAddress()->getRegion()) ?>" title="<?php echo $this->__('State/Province') ?>" class="input-text" style="display:none" /></div></code></div>

Abstract.php
Comment out:

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<div><code> if ($this->getCountryModel()->getRegionCollection()->getSize()  && !Zend_Validate::is($this->getRegionId(), 'NotEmpty')) {  $errors[] = $helper->__('Please enter state/province.');  } </code></div> <div>

opcheckout.js
There are a few code-blocks you have to comment out.
Around line 330:

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<div><code> if (window.billingRegionUpdater) {  billingRegionUpdater.update();  }</code></div> <div>

Around line 440:

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<div><code> shippingRegionUpdater.update();  $('shipping:region_id').value = $('billing:region_id').value;  $('shipping:region').value = $('billing:region').value;  //shippingForm.elementChildLoad($('shipping:country_id'), this.setRegionValue.bind(this)); </code></div>

Around line 450:

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<div><code> setRegionValue: function(){  $('shipping:region').value = $('billing:region').value;  },</code></div> <div>

Around line 490:

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<div><code> if (window.shippingRegionUpdater) {  shippingRegionUpdater.update();  } </code></div> <div>