Microsoft

Studio Mektek has released a free version of Mechwarrior 4. http://www.mektek.net/projects/mw4/ This was done fully in conjunction with Microsoft and Smith & Tinker.

Combining three top-selling titles, Zoo Tycoon: Complete Collection includes the original Zoo Tycoon game and the Dinosaur Digs and Marine Mania expansion packs, allowing players’ imaginations to run wild as they care for more than 100 land, aquatic and prehistoric animals in the most beautiful and lively zoo imaginable. Additionally, Zoo Tycoon: Complete Collection comes with loads of bonus content, including the entire new Endangered Species Theme Pack.

This game is an action RPG with a top-down perspective. Players can recruit additional NPCs to expand the size of their party. Character development is based upon skill points which allows for customization of abilities. Take Dungeon Siege. Take Diablo II. Mix together. Serve chilled.

Age of Mythology is an RTS set within the major historical mythologies - Greek, Roman, Egyptian. It is in the same play style as Age of Empires II, and with good reason. AOM is from the same developer, and same "series" as AOE2.
From Ensemble Studios, the creators of Age of Empires and Age of Kings, comes Age of Mythology, a game that transports players to a time when heroes did battle with monsters of legend and the gods intervened in the affairs of mortal men.

Players control a large party of characters as they fight their way through a seamless environment. Characters develop their abilities by using a particular class of weapon or magic. Players can customize their characters to suit their playing style. Slash, burn, kill, loot. Rinse and repeat.

FS 2004 is the 2003 release in the venerable flight sim series from Microsoft. This release celebrates 100 years of flight.

Asheron's Call is a massively multiplayer online roleplaying game. The original Asheron's Call release was in November 1999, followed by an expansion pack in 2001 (AC: Dark Majesty), and most recently in 2005 (AC: Throne of Destiny). While players aren't required to purchase the latest expansion pack, players are required to install the graphics update that shipped after this expansion. This graphics update included support for DirectX 9.0 and more flexible monitor resolutions.