Ninety-Nine Nights will NOT need a hard drive.

Turns out that the "Hard Drive required" sign on Xbox.com turned out to be nothing more than a mistake on Microsoft's behalf. They did not mean to put up that it required a hard drive on the website and has now been taken down.
The game will be playable for those of you who do not own a hard drive. There was speculation if it would be required or not. Looking to the Japanese version of the game which was released in Japan awhile ago did no good since there are no Core packages for Japanese consumers.

360-HQ,
Loki

News-Source:Gamer Score Blog