I mentioned earlier that the Xbox 360 now has a one year warranty. I also read on the Xbox forums that there was a little confusion WRT how extended warranties purchased by customers would be recognized.
Well, I received a confirmation today from the Xbox team that, for customers who purchased an extended warranty on their Xbox 360, the warranty extension they purchased (the one- or two-year extension, I think) will take effect after the first year. So, my understanding is that customers who purchased a two-year extended warranty will now be covered for a total of three years from the date of purchase.
I believe that the Xbox team will make this more clear on the web site and the warranty pages in the near future. Hope this helps.