Developers in russia were creating a Halo for PC when it got leaked on the internet by accident and a group of people took it upon themselves to maintain it and update it, naming it ElDewrito.
Google Doc on how to install
Its a pretty good quality game with no bugs for being free and updated by amateurs, it would be great if more people played. You can enjoy all the pleasantries of all the Halo's combined, online, and on PC.
I have not seen it mentioned here so I thought I would bring it up. Not too many hackers yet, an aimbot was made awhile ago but stopped being updated.
If anyone has any issues installing it I'll be here to help.