If you have an Xbox 360 Slim/4GB model unfortunately you will not be able to install the game.
Need for Speed Rivals on the Xbox 360 requires an Xbox 360 Hard Drive with 3GB of storage space for a mandatory installation of game disc content. you will be prompted to perform this installation the first time time you boot up your game.
You cannot play your game without this installation, nor can it be installed on flash memory sticks, or internal flash memory--such as the internal memory of the Xbox 360 Slim, or 4GB model. Hard Drives are available and sold separately for the Xbox 360 Slim/4GB, Arcade, and Core consoles.
