The Microsoft Windows retail-release includes all previously released official downloadable content available for Oblivion:
•Horse Armor Pack (DLC1)
•Orrey (DLC2)
•Wizard's Tower (DLC3)
•The Thieves Den (DLC7)
•Mehrunes Razor (DLC9)
•The Vile Lair (DLC5)
•Spell Tomes (DLC4)
•Knights of the Nine (DLC8)
All other versions are just for the Knights of the Nine expansion:
Knights of the Nine centers on a faction of the same name, devoted to locating and preserving a set of "Crusaders' Relics". Once found, these relics must be used to defeat the sorcerer-king Umaril, who seeks revenge on the Nine Divines.
Knights of the Nine is identical to the gameplay of Oblivion; the basic design, maneuvers, and interfaces remain unchanged. As such, it is a fantasy-based role-playing adventure game. Players begin Oblivion by defining their character; deciding on its skill set, specialization, physical features, and race. Knights of the Nine is an example of open-ended-style gameplay: the main quest may be delayed or completely ignored as the player explores the game world, follows side quests, interacts with NPCs, and develops a character according to their taste.