I recently had to take advantage of the extended warranty that the 360 had to offer. I got the news here on the Big Orange Machine and an email with the number to customer service. In about 15 minutes they had my serial number down and a box shipping over to my house so they can repair problems I have had with reading discs.
I hate, and I mean hate customer service with a passion, but this was so easy I recommend doing it to anyone still in the time frame having the slightest problem with their box. I will however be out of an Xbox for three weeks, as such I’ll Game Fly Final Fantasy XI and give it a run.