You can view the Warthog in the Forza 4 autovista mode. You must be thinking of driving it in the game but unfortunately that isn’t possible. You can use the Kinect to explore the vehicle from the legendary Halo series. Instead of Jeremy Clarkson, it will be Cortana that will be narrating about the vehicles specifications and abilities.
The game releases on October 11th exclusively for the Xbox 360.