Magento: Delete all orders

Run the below Sql Script to your database for delete all orders

SET FOREIGN_KEY_CHECKS=0;
TRUNCATE `sales_flat_order`;
TRUNCATE `sales_flat_order_address`;
TRUNCATE `sales_flat_order_grid`;
TRUNCATE `sales_flat_order_item`;
TRUNCATE `sales_flat_order_status_history`;
TRUNCATE `sales_flat_quote`;
TRUNCATE `sales_flat_quote_address`;
TRUNCATE `sales_flat_quote_address_item`;
TRUNCATE `sales_flat_quote_item`;
TRUNCATE `sales_flat_quote_item_option`;
TRUNCATE `sales_flat_order_payment`;
TRUNCATE `sales_flat_quote_payment`;
TRUNCATE `sales_flat_shipment`;
TRUNCATE `sales_flat_shipment_item`;
TRUNCATE `sales_flat_shipment_grid`;
TRUNCATE `sales_flat_invoice`;
TRUNCATE `sales_flat_invoice_grid`;
TRUNCATE `sales_flat_invoice_item`;
TRUNCATE `sales_flat_creditmemo`;
TRUNCATE `sales_flat_creditmemo_comment`;
TRUNCATE `sales_flat_creditmemo_grid`;
TRUNCATE `sales_flat_creditmemo_item`;
TRUNCATE `sendfriend_log`;
TRUNCATE `tag`;
TRUNCATE `tag_relation`;
TRUNCATE `tag_summary`;
TRUNCATE `wishlist`;
TRUNCATE `log_quote`;
TRUNCATE `report_event`;

ALTER TABLE `sales_flat_order` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_order_address` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_order_grid` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_order_item` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_order_status_history` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote_address` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote_address_item` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote_item` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote_item_option` AUTO_INCREMENT=1;
ALTER TABLE `sendfriend_log` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_order_payment` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_quote_payment` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_shipment` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_shipment_item` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_invoice` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_invoice_grid` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_invoice_item` AUTO_INCREMENT=1;
ALTER TABLE `sales_flat_shipment_grid` AUTO_INCREMENT=1;
ALTER TABLE `tag` AUTO_INCREMENT=1;
ALTER TABLE `tag_relation` AUTO_INCREMENT=1;
ALTER TABLE `tag_summary` AUTO_INCREMENT=1;
ALTER TABLE `wishlist` AUTO_INCREMENT=1;
ALTER TABLE `log_quote` AUTO_INCREMENT=1;
ALTER TABLE `report_event` AUTO_INCREMENT=1;
SET FOREIGN_KEY_CHECKS=1;

For Particular orders

• From  Admin=>Sales=>Orders
• Note down your test orders ids for example 100000001,100000002,100000003
• Now create a custom php file in magento root directory and name it: remove_orders.php
• Copy and paste the following code in that file.

<?php
require 'app/Mage.php';
Mage::app('admin')->setUseSessionInUrl(false);                                                                                                                 
//replace your specific orders numbers here like:
$test_order_ids=array(
  '100000001',
  '100000002',
  '100000003'
);
foreach($test_order_ids as $id){
    try{
        Mage::getModel('sales/order')->loadByIncrementId($id)->delete();
        echo "order #".$id." is removed".PHP_EOL;
    }catch(Exception $e){
        echo "order #".$id." could not be remvoved: ".$e->getMessage().PHP_EOL;
    }
}
echo "complete."
?>

Note: Delete that file after completing task.