If it is less than 12 months old, take it back to the shop where you bought it, that is if you bought it in a shop and not online.
They are responsible (the shop) and
not Microsoft. Sending it to Microsoft means you will just get a referb, so it could be nice and new-ish or it could be 10 times more battered than your current one, just had a new part in it and quite likely to go wrong again. In addition, getting a referb means you will only have a 3 month warranty on it (I think) whereas if you got a replacement in the shop if/where you bought it, you will have a full 12 months as it is a brand spanking new product.
Also, if you take it back you could have a replacement there and then instead of having to wait for Microsoft to fanny around with it.!