This is from Tropicana Twister Xbox prize promotion.
Just register and even if you don't win the grand prize, you still get a complimentary 48-hour Xbox Live Trial.
You can do this as many times as you like, as long as you enter a different email each time.
Ive gotten around 30 codes so far from this.
access code AA4XPN3
disposable emails http//www.mailinator.com/
Remember these codes are not stackable, you can only use the next code after the other has expired.