The helicopter arrived at Mildura at about 1745 EST. The pilot was marshalled to a parking spot by the refueller. After the helicopter was refuelled, the pilot offered to reposition the helicopter but the refueller suggested it remain parked where it was, as had been common practice in the past. The pilot complied with the refueller's advice. The helicopter was not parked on a taxiway. At 2045 EST, while taxiing to the terminal, in very dark conditions, the Cessna 404 pilot followed a yellow taxi guide line with the aircraft's taxy light illuminated. He was momentarily distracted by the windsock lights flashing and inadvertently allowed the aircraft to drift about one metre to the right. As he returned his attention to the yellow line, he suddenly saw the parked helicopter in his peripheral vision. He attempted to stop but the right propeller contacted one rotor blade and the right wing tip impacted the windshield of the unattended helicopter. The collision occurred about 25 metres from the usual parking bay for the Cessna. The Cessna 404 pilot was not expecting a helicopter to be parked where it was.