Do i need to enable/disable register global by going through php.ini ?
Register_globals should be disabled, see system requirements for X-Cart v4.5.5 and later : http://help.x-cart.com/index.php?title=X-Cart:Server_Requirements_%28X-Cart_4.5%29#PHP_configuration
To answer the other questions, some more info is required, in particular, what x-cart version you use.
I recommend that you send your question ( and specify the version + store URL) to support@x-cart.com.