For a refund, you have only 10 days from the Apple Store B&M.. You have a defective machine which is a repair/replace issue. The time limit on that is a year (not counting extended Applecare plans). Since it is really quite a short time since your purchase, meaning less than 30 days, I would go back to the Apple Store you bought it from and take it to the Genius counter and politely explain your problem. Make it clear that you need your computer for your work etc.. and that you don't have a backup and really need them to exchange it. I feel that you have a 90% chance that they would just swap it for you on the spot. Your chances go down to 30% if you go in aggresively etc..