Free 2 gold trail in box works?

well, i recently upgraded to high-speed internet and made an account for xbox live. I procede to enter my free 2 day trail code and it says its invalid. help?

your entering the correct code, right? it should be something like this —> 3kl5-kj3j-35kj-2l3k <— NOTE: this was random, not an actual code.