Help with Fable 3 game, please!?

So, about a month ago I bought the game, installed it on my computer, and loved every minute I played it :), now, though I have a new computer, the disk, and no box... is there a way I can get my serial, or get a new one through the website or something, I don't want to pay another 40 bucks for the game... someone help, even if you give me a working code I don't care anymore lol. Thanks for any help!