redrain85: Here are some things you can try:
1. Reduce the Mouse Sensitivity and Mouse Smoothing options in the game to their minimum settings: Options > Controls > Mouse.
2. Limit the frame rate to 99 FPS or less, using something like MSI Afterburner/RivaTuner Statistics Server. (Though RTSS won't limit the frame rate unless you turn off Windows XP SP2 compatibility on Lithtech.exe.)
3. Disable the "Enhance pointer precision" option in Windows:
https://www.tenforums.com/tutorials/101691-turn-off-enhance-pointer-precision-windows.html 4. Reduce your Mouse polling rate to 125 Hz. (I know you've already done that, but I'm including it for others who might read this.)
5. Lower your Mouse DPI. (I have mine set to 2400 DPI.)
6. Try the NoDTToDITMouseBatch registry compatibility fix, by following the instructions in the "Let me fix it myself" section (you'll have to copy and paste the entire link into your browser's address bar, this doesn't work if you click on it):
https://web.archive.org/web/20150219194409/https://support.microsoft.com/kb/2908279 I don't recommend this if anyone isn't comfortable with modifying the Windows Registry. Also, if a registry key for Lithtech.exe already exists, it's important to add the value "NoDTToDITMouseBatch" to the key and not replace what's already there.
Out of all of these: I would say 1, 2, and 5 are the most likely to help. Especially 2. The game simply wasn't designed with frame rates in mind that modern hardware is now capable of producing.
Attempted the fixes, but no dice.
There really needs to be a mod to be created for this game to allow for raw mouse input, or something else.
I appreciate the help, but this game has some jank that needs serious retooling.\
The odd thing is this worked completely fine last time, it just suffered from the mouse having a hard time trying to recognize diagonal movement, now it can't stop detecting diagonals when i'm not try to do such angles.
Again, thanks for helping, but this needs a true be all end all fix asap.