[UPDATE] Following the publication of this story, a Microsoft representative confirmed with GameSpot that it has no plans to release any Halo games on Steam.
The original story follows below.
Microsoft's 2007 first-person shooter Halo 3 could be on its way to the PC. A NeoGAF user tapped into xPaw's Steam Database and found Halo 3--along with many other titles--in the Steam registry, suggesting they could be released for the PC in the future.
On the list are previously confirmed-for-PC games like Resident Evil: Revelations, but also a host of titles not yet announced for the PC. These include Fez, Quantum Conundrum 2, The King of Fighters XIII, Second Life, and Duke Nukem 3D, among others.
This information is by no means a confirmation that Halo 3--or any of the other titles--are indeed coming to the PC. These listings could relate to Steam Community hubs for non-Steam games, or something else entirely.
A Microsoft representative was not immediately available to comment.
If Halo 3 does come to the PC, it will not be the first entry in the franchise to do so. Halo: Combat Evolved and Halo 2 are both currently available for the PC, though subsequent entries Halo 3: ODST, Halo: Reach, and Halo 4 are currently Xbox 360 exclusives.