Indexer model is not defined.

Trace:
#0 E:\xampp\htdocs\magentoStore\includes\src\Mage_Index_Model_Process.php(310): Mage::throwException('Indexer model i...')
#1 E:\xampp\htdocs\magentoStore\includes\src\Mage_Index_Block_Adminhtml_Process_Grid.php(78): Mage_Index_Model_Process->getIndexer()
#2 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Widget_Grid.php(534): Mage_Index_Block_Adminhtml_Process_Grid->_afterLoadCollection()
#3 E:\xampp\htdocs\magentoStore\includes\src\Mage_Index_Block_Adminhtml_Process_Grid.php(64): Mage_Adminhtml_Block_Widget_Grid->_prepareCollection()
#4 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Widget_Grid.php(626): Mage_Index_Block_Adminhtml_Process_Grid->_prepareCollection()
#5 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Widget_Grid.php(632): Mage_Adminhtml_Block_Widget_Grid->_prepareGrid()
#6 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2540): Mage_Adminhtml_Block_Widget_Grid->_beforeToHtml()
#7 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2260): Mage_Core_Block_Abstract->toHtml()
#8 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2204): Mage_Core_Block_Abstract->_getChildHtml('grid', true)
#9 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Widget_Grid_Container.php(77): Mage_Core_Block_Abstract->getChildHtml('grid')
#10 E:\xampp\htdocs\magentoStore\app\design\adminhtml\default\default\template\widget\grid\container.phtml(36): Mage_Adminhtml_Block_Widget_Grid_Container->getGridHtml()
#11 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3336): include('E:\xampp\htdocs...')
#12 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3367): Mage_Core_Block_Template->fetchView('adminhtml\defau...')
#13 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3381): Mage_Core_Block_Template->renderView()
#14 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Template.php(81): Mage_Core_Block_Template->_toHtml()
#15 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Widget_Container.php(308): Mage_Adminhtml_Block_Template->_toHtml()
#16 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2541): Mage_Adminhtml_Block_Widget_Container->_toHtml()
#17 E:\xampp\htdocs\magentoStore\includes\src\__default.php(13451): Mage_Core_Block_Abstract->toHtml()
#18 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2541): Mage_Core_Block_Text_List->_toHtml()
#19 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2260): Mage_Core_Block_Abstract->toHtml()
#20 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2204): Mage_Core_Block_Abstract->_getChildHtml('content', true)
#21 E:\xampp\htdocs\magentoStore\app\design\adminhtml\default\default\template\page.phtml(74): Mage_Core_Block_Abstract->getChildHtml('content')
#22 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3336): include('E:\xampp\htdocs...')
#23 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3367): Mage_Core_Block_Template->fetchView('adminhtml\defau...')
#24 E:\xampp\htdocs\magentoStore\includes\src\__default.php(3381): Mage_Core_Block_Template->renderView()
#25 E:\xampp\htdocs\magentoStore\includes\src\Mage_Adminhtml_Block_Template.php(81): Mage_Core_Block_Template->_toHtml()
#26 E:\xampp\htdocs\magentoStore\includes\src\__default.php(2541): Mage_Adminhtml_Block_Template->_toHtml()
#27 E:\xampp\htdocs\magentoStore\includes\src\__default.php(27704): Mage_Core_Block_Abstract->toHtml()
#28 E:\xampp\htdocs\magentoStore\includes\src\__default.php(13844): Mage_Core_Model_Layout->getOutput()
#29 E:\xampp\htdocs\magentoStore\app\code\core\Mage\Index\controllers\Adminhtml\ProcessController.php(55): Mage_Core_Controller_Varien_Action->renderLayout()
#30 E:\xampp\htdocs\magentoStore\includes\src\__default.php(13872): Mage_Index_Adminhtml_ProcessController->listAction()
#31 E:\xampp\htdocs\magentoStore\includes\src\__default.php(18234): Mage_Core_Controller_Varien_Action->dispatch('list')
#32 E:\xampp\htdocs\magentoStore\includes\src\__default.php(17768): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#33 E:\xampp\htdocs\magentoStore\includes\src\__default.php(20368): Mage_Core_Controller_Varien_Front->dispatch()
#34 E:\xampp\htdocs\magentoStore\app\Mage.php(683): Mage_Core_Model_App->run(Array)
#35 E:\xampp\htdocs\magentoStore\index.php(88): Mage::run('', 'store')
#36 {main}

To see whats wrong with the system:

Open the page:

includes\src\Mage_Index_Model_Process.php

In the function “public function getIndexer()”, find the below line:

Mage::throwException(Mage::helper('index')->__('Indexer model is not defined.'));

Add add this debug line, just before the line:

echo $code;exit;

and try to access the index page again. This should show you the module or reason which is creating problems. Look specially in the extensions that you recently installed.

Please post you comments in case you face any issue.