If you had already sent one in and they made you pay for it, you will be entitled to a refund, as long as you are still within one year of your purchase date.
Originally Posted by XBox.com
Effective today (December 22), the one year warranty is now the standard for all Xbox 360 consoles. Customers that experience hardware issues with their Xbox 360 within one year of purchase will have their consoles repaired at no cost. Moreover, the new warranty policy is retroactive, so consumers that may have already paid for out-of-warranty Xbox 360 repair within one year of the console's purchase will be eligible for reimbursement of their console repair charges.