Halo 2 Reclaimed aims to restore the Vista port of the Halo 2 campaign back to its Original Xbox state as much as possible through the limited modding capabilities of Halo 2 Vista.
In the works on and off for a year, we've finally completed the first release of Halo 2 Reclaimed, a community project to restore Halo 2's campaign, best used with Project Cartographer. Much like the Gearbox port for Halo CE, since 2007, the only version of Halo 2 that PC gamers have been able to experience is the Vista port, a version of the game that is not a faithful representation of the original, down to the gameplay itself. Increasing the tick rate from 30 to 60 produced multiple issues. Sped up firing rates, faster firing enemies, with more aggressive firing behaviors, and a number of visual and audio bugs were also introduced.
The Reclaimed project aims to not only make the game feel more like its original counterpart, it also aims to help show you how to setup Halo 2 Vista to be the best it can be. With the release of Halo 2 Anniversary near, Reclaimed provides a way to preserve the original experience for those without an Original Xbox, and to remind people of the issues that Halo 2 Anniversary (which still uses H2V as a base) still has. Not everything has been fixed yet in Reclaimed. A version for the MCC is planned, and will be done if possible.
All up to date details in the documentation document: 1drv.ms