Are you getting any red lights? (Ring of Death
?)
If so, they extended the warranty to 3 years for that.
If not, make sure all cables are plugged in, try putting the Xbox 360 Vertical (or Horizontal, whichever is the opposite of what you had). And try to turn it on.
If it does not work call em up and explain the issue.
You'll most likely get a refurbished one back