Unfortunately Magento does not have the function built into its setup to allow you the option to change a products attribute set once you have created a simple product. However, with the following coding updates, you can add the functionality to change a simple products attribute set directly on the Catalog > Manage Products page:

In app/code/core/Mage/Adminhtml/Block/Catalog/Product/Grid.php around line 253 ad:

$sets = Mage::getResourceModel(‘eav/entity_attribute_set_collection’)
->setEntityTypeFilter(Mage::getModel(‘catalog/product’)
->getResource()->getTypeId())->load()->toOptionHash();

array_unshift($statuses, array(‘label’=>”, ‘value’=>”));
$this->getMassactionBlock()->addItem(‘attribute_set’, array(
‘label’=> Mage::helper(‘catalog’)->__(‘Change attribute set’),
‘url’ => $this->getUrl(‘*/*/massAttributeSet’, array(‘_current’=>true)),
‘additional’ => array(
‘visibility’ => array(
‘name’ => ‘attribute_set’,
‘type’ => ‘select’,
‘class’ => ‘required-entry’,
‘label’ => Mage::helper(‘catalog’)->__(‘Attribute Set’),
‘values’ => $sets
)
)
));

And then in app/code/core/Mage/Adminhtml/controllers/Catalog/ProductController.php (anywhere in the class) add a new function:

public function massAttributeSetAction(){

$productIds = $this->getRequest()->getParam(‘product’);
$storeId = (int)$this->getRequest()->getParam(‘store’, 0);
if(!is_array($productIds)) {
$this->_getSession()->addError($this->__(‘Please select product(s)’));
} else {
try {
foreach ($productIds as $productId) {
$product = Mage::getSingleton(‘catalog/product’)
->unsetData()
->setStoreId($storeId)
->load($productId)
->setAttributeSetId($this->getRequest()->getParam(‘attribute_set’))
->setIsMassupdate(true)
->save();
}
Mage::dispatchEvent(‘catalog_product_massupdate_after’, array(‘products’=>$productIds));
$this->_getSession()->addSuccess(
$this->__(‘Total of %d record(s) were successfully updated’, count($productIds)));
} catch (Exception $e) {
$this->_getSession()->addError($e->getMessage());
}
}

$this->_redirect(‘*/*/’, array(‘store’=>(int)$this->getRequest()->getParam(‘store’, 0)));
}

Once you have added the two snippets of code you will now be able to select products from teh Manage Products list and update any products Attribute Set from the actions dropdown menu.

Simply Select ‘Change Attribute Set’ and select the appropriate attribute set from the new dropdown menu that appears to the right of Actions.