Step 1. Make sure, that the var/locks folder is writable
Step 2. Delete all the .locks file from the var/locks and then try to reindex the data again if it works then it is OK otherwise follow the steps below
Step 3. Run the following MySQL Queries through the PHPMyadmin (Before running these commands take backup of database before running the SQL query. )
ALTER TABLE catalog_category_entity ENGINE=INNODB; ALTER TABLE core_store ENGINE=INNODB; DELETE FROM catalog_category_product_index; DELETE cpop.* FROM catalog_product_option_price AS cpop INNER JOIN catalog_product_option AS cpo ON cpo.option_id = cpop.option_id WHERE cpo.type = 'checkbox' OR cpo.type = 'radio' OR cpo.type = 'drop_down'; DELETE cpotp.* FROM catalog_product_option_type_price AS cpotp INNER JOIN catalog_product_option_type_value AS cpotv ON cpotv.option_type_id = cpotp.option_type_id INNER JOIN catalog_product_option AS cpo ON cpotv.option_id = cpo.option_id WHERE cpo.type <> 'checkbox' AND cpo.type <> 'radio' AND cpo.type <> 'drop_down'
Now try to reindex the data from the Magento admin Panel. If it is reindexed all the data successfully then it is Ok otherwise repairing the database. For repairing the database you can download the repairing tool from HERE
Hope this will help to someone.