Straight from the Lions mouth.

http://www.starwars.com/movies/saga/20080826news.html

Returning to store shelves on November 4th are the six episodes of the Star Wars saga on DVD bundled in convenient trilogy sets. Perfect for gift-giving as the holidays approach, the Prequel Trilogy set includes Episodes I-III, while the Star Wars Trilogy includes Episodes IV-VI.

Fans who already own the prequel trilogy double-disc releases (released from 2001-2005) and the Star Wars trilogy double-disc releases (released in 2006) already have all the content that's available in this set. There's nothing new in this set you don't already have. But for friends and family still looking to fill in these gaps in their DVD collections, these sets make it easy and affordable to complete the saga.

also here as well.

http://starwars.wikia.com/wiki/Original_unaltered_trilogy_(DVD)