First of all make sure you use a registered service to return the laptop. Use one that you can track online because then you know that they have received it. I am presuming that you paid by credit card ( not debit card ).If the refund is slow in coming then speak to your credit card company. They can achieve in hours what it takes an individual days to do.
Allow the company 48 hours from time of receipt of faulty goods to process the refund before you initiate any form of action.