Currently Being ModeratedApr 26, 2012 7:05 AM (in response to wake2010)
You can only redownload content via your Purchased page. If the item doesn't appear on your Purchased page, it is not eligible for redownload.
To learn how to download past purchases, visit this article:
Downloading past purchases from the App Store, iBookstore, and iTunes Store
That said, movies are only eligible for redownload in the United States, and if the movie has been modified in the iTunes Store since you purchased it, it will not appear on your Purchased page and isn't eligible for subsequent download.
Additionally, some movies you’ve previously purchased may not be available for download, even if they haven't been modified. You will see the message "When purchased, this movie will not be available from iTunes in the Cloud” if the movie can't be downloaded again. This message appears under the Buy button on the iTunes store product page.
To learn what previously purchased content is available for download in your country, visit this article:
iTunes in the Cloud and iTunes Match Availability