DURING THE TAKEOFF ROLL, THE AIRLANE COLLIDED WITH A GENERATOR THAT WAS POSITIONED ON THE RUNWAY TO ILLUMINATE AN X INDICATING THAT THE RUNWAY WAS CLOSED. THE PILOT DID NOT REALIZE THAT THE RUNWAY WAS CLOSED EVEN AFTER LISTENING TO AN ATIS MESSAGE STATING THAT THE RUNWAY WAS CLOSED. A NOTAM WAS IN EFFECT REPORTING THE SAME. THE PILOT SAID HE HEARD WHAT HE EXPECTED TO HEAR WHEN HE 'LISTENED' TO THE ATIS.