A twin Cessna collided with a single engine Cessna from the single engine Cessna's 7 o'clock position. The single engine Cessna crashed and the twin Cessna landed without further incident. Both airplanes were conducting visual flight rules personal flights to Van Nuys, CA. The single engine Cessna 172 was receiving traffic advisories from Burbank TRACON. The twin engine Cessna had departed Fullerton and was flying a circuitous route to Van Nuys in order to avoid the airport radar service area. The single engine Cessna was transponder equipped but without Mode C capability. The twin engine Cessna was equipped with, and using, a transponder with Mode C capability. The radar data study revealed that the twin engine Cessna was displayed on the controller's radar scope for about 4 minutes before the collision. The controller did not warn the single engine Cessna pilot of the converging traffic. The TRACON was not programmed to alert the controller of a conflict between a tracked (C-172) and untracked (C-411) target.