Found this information on the FAQ section of Apples support pages with regards to movie rental
PITY THEY DONT TELL US THIS INFORMATION WHEN THEY ADVERTISE RENTED FILMS.
IT WOULD APPEAR IF DOWNLOADED ON AN I PAD IT CANNOT BE TRANSFERED TO A PC
THATS NOT WHAT THE ADVERT FOR RENTING MOVIES STATES!
If you download a rented movie on your computer: You can transfer it to a device such as your Apple TV (1st generation), iPhone, iPad, or iPod if it’s a standard-definition film (movies in HD can only be watched on your computer, iPad, iPhone 4 or later, iPod touch (4th generation or later), or Apple TV). Once you move the movie from your computer to a device, the movie will disappear from your computer's iTunes library. You can move the movie between devices as many times as you wish during the rental period, but the movie can only exist on one device at a time.
If you download a rented movie on your iPhone 4 or later, iPad, iPod touch (4th generation or later), or Apple TV: It is not transferable to any other device or computer.