Why are you reviving a year old topic? And what does inversion have to do with raw mouse input? That setting is in the cartographer setting menu or halo2config1.ini
It just happened today today. I searched for anyone else having similar. There is only a halo2config.exe file and the raw input is what messes with the halo abiity to change mouse look functions.The 'invert look' suddenly does not work, so the game is hard to play. Still cannot turn it off. Or change mouse orientation in halo2.
Update: after several hours, I uninstalled halo2 and went thru the initial target check on starting a new campaign. After three tries, I got the mouse inverted correctly. It is a BUG. I have dealt with soft bugs for years and this is the latest.