Halo: Combat Evolved released in fall 2003 for PC. Bungie has moved on—but the community keeps the game alive through mods. Take SPV3, for example.
SPV3 is an ongoing mod that not only enhances the graphics of the original Halo, it also adds new weapons, new enemies, new vehicles, revised and extended levels/environments, and even armor upgrades from the newer games. Amazing. You can see all of of this in action in the trailer above.
The release date varies...
...but everything will be out by the end of 2014. You can keep up with the mod's development here.