Microsoft has confirmed the existence of a Halo-related project titled 'Bootcamp', which surfaced recently via Korean Ratings.
Little else can be gleaned from the Google-translation, but a Microsoft rep was surprisingly willing to confirm the prematurely outed project with an albeit vague statement.
"What's Bootcamp? It is not related to our Xbox One efforts, or the Reclaimer Saga, but rather a project we're very enthusiastic about and will have more to say about in the near future," said the rep.
The 'Reclaimer Saga' refers to the second Halo trilogy, which is expected to continue on the next-gen Xbox One console.
A PC port of Halo 3 would seem unlikely at this point - a full six years after it originally hit Xbox 360 - unless it were some sort of experimental free-to-play multiplayer venture (think Quake Live). The project may also be related to a Halo novel by Reed Ruiz titled Halo: Fall of Reach: Boot Camp, but nothing is confirmed.
Perhaps we'll hear more on this at E3 next month.