I just got a Vista Ultimate cd from a college school, but it is an update copy. You can only activate it once and since I am keeping this computer for a long time, I want a legit copy. (I am using Boot Camp on a Mac)

Does it still work if i I install it with the cd and use the update key, or should I get one from a torrent site and then use the key from the cd to make it legal?

Help appreciated