Emprex external DVD, going internal ?

Question

My friend has a external Emprex DVD burner. He wanted it putting into his pc so after carefully dismantling the casing and freeing the DVD i put it in the PC. It took ages before the thing would repond (open) and after about 20 mins of changing power cables it started playing ball. Now though (3 weeks later) it has started to continuesley open and close. he has done a spyware sweep that found nothing and he has just rung to say it is not even opening now even though the lights are flashing.